The safe won't open using the right combination and the key. The lever won't go down.

notify manufacturer or a locksmith

Our tech team at Quality gun safes wall safes and floor safes store in Burlingame Ca produced this video

A1 Locksmith Google

Help may be found at this site...
http://www.paragonlockandsafe.com/index.php?option=com_content&view=article&id=21&Itemid=110

Because you lost the combination of it, you can't use it with your keys alone.

3 Digit Combination Lock
31-10-31

1. NOTE: If your safe DOES NOT have a key, skip Step 3.
   
2. Turn the dial to zero.
   
3. Insert your key and turn it until the plunger pops out.
   
4. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
5. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
6. Turn the dial to the left to the last number (stop the first time on your last number).
   
7. 
   Pull the handle down; the door should open.

3 Digit Combination Locks for Security Safes
31-10-31

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
3. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
4. Turn the dial to the left to the last number (stop the first time on your last number).
   
5. Insert the key; turn right.
   
6. 
   Pull on the key while it's in the lock to open the door.

3 Digit Combination Locks for Gun Safes
31-10-31

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
3. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
4. Turn the dial to the left to the last number (stop the first time on your last number).
   
5. 
   Pull the handle down; the door should open.

Electronic Locks
31-10-31

1. Insert the tubular key into the lock to the left of the key pad.
   
2. Turn the key all the way to the right until the plunger pops out.
   
3. Press the five-digit factory code. The green Proceed light will come on.
   
4. Pull the handle down; the door should open.

4 Digit Combination Lock
31-10-31-10

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) four times to the first number of the combination (pass the first number of your combination three times, stopping on it the fourth time).
   
3. Turn the dial to the right (clockwise) three times to the second number of the combination (pass your second number twice, stopping on it the third time).
   
4. Turn the dial to the left (counterclockwise) two times to the third number of the combination (pass the third number of your combination one time, stopping on it the second time).
   
5. Turn the dial to the right to the last number (stop the first time on your last number).
   
6. Pull the handle down; the door should open.

You can find more information on your Sentry Safe at www.SentrySafeShop.com

3 Digit Combination Lock
31-10-31

1. NOTE: If your safe DOES NOT have a key, skip Step 3.
   
2. Turn the dial to zero.
   
3. Insert your key and turn it until the plunger pops out.
   
4. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
5. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
6. Turn the dial to the left to the last number (stop the first time on your last number).
   
7. 
   Pull the handle down; the door should open.

3 Digit Combination Locks for Security Safes
31-10-31

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
3. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
4. Turn the dial to the left to the last number (stop the first time on your last number).
   
5. Insert the key; turn right.
   
6. 
   Pull on the key while it's in the lock to open the door.

3 Digit Combination Locks for Gun Safes
31-10-31

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) three times to the first number of the combination (pass the first number of your combination two times, stopping on it the third time).
   
3. Turn the dial to the right (clockwise) two times to the second number of the combination (pass your second number once, stopping on it the second time).
   
4. Turn the dial to the left to the last number (stop the first time on your last number).
   
5. 
   Pull the handle down; the door should open.

Electronic Locks
31-10-31

1. Insert the tubular key into the lock to the left of the key pad.
   
2. Turn the key all the way to the right until the plunger pops out.
   
3. Press the five-digit factory code. The green Proceed light will come on.
   
4. Pull the handle down; the door should open.

4 Digit Combination Lock
31-10-31-10

1. Turn the dial to zero.
   
2. Turn the dial to the left (counterclockwise) four times to the first number of the combination (pass the first number of your combination three times, stopping on it the fourth time).
   
3. Turn the dial to the right (clockwise) three times to the second number of the combination (pass your second number twice, stopping on it the third time).
   
4. Turn the dial to the left (counterclockwise) two times to the third number of the combination (pass the third number of your combination one time, stopping on it the second time).
   
5. Turn the dial to the right to the last number (stop the first time on your last number).
   
6. Pull the handle down; the door should open.

You can find more information about your Sentry Safe at www.SentrySafeShop.com

Locksmiths advise these Opening instructions for sentry fireproof electronic security safes. Insert the tubular sentry key into the lock to the left of the key pad. Turn the key all the way to the right until the plunger pops out. Press the five-digit factory code. The green Proceed light will come on. Pull the handle down; to crack the sentry door open.

sentry safes opening instructions for 4 # combo locks
Turn the dial to zero.
Turn the dial to the left (counterclockwise) four times to the first number of the combination (pass the first number of your combination three times, stopping on it the third time).
Turn the dial to the right (clockwise) three times to the second number of the combination (pass your second number twice, stopping on it the third time).
Turn the dial to the left (counterclockwise) two times to the third number of the combination (pass the third number of your combination one time, stopping on it the second time).
Turn the dial to the right to the last number (stop the first time on your last number).
Pull the handle down to crack the sentry safe open.

Instructions:
Opening the key storage
compartment door
1. Open shutter door to reveal the dials
and the release button
2. Rotate dials to the current combination
(if the lock is new, the combination is set
at the factory to 0-0-0-0)
3. Press down on the release button
to open the door
4. Pull the door fully open
5. Add or remove keys
6. Close compartment door
7. Scramble the combination dials to lock
the door and conceal your combination (A)
8. Close the shutter door (B)
To set a new combination:
The initial combination is set at the
factory to 0-0-0-0
1. Open the compartment door
(see instructions above)
2. Push the reset lever left and down.
The lever remains in this position
3. Rotate dials to your desired combination
4. Push the reset lever, up and right, back
to the original position
5. Close the key storage compartment door
6. Scramble the combination dials to lock
the door and conceal your combination (A)
7. Close the shutter door (B)
To hang shackle model
1. Open the compartment door
(see instructions above)
2. Push the shackle release lever to the left
to open shackle
3. Pull the shackle up and out of the lock
4. Place shackle around door knob or other object
5. Close shackle to lock
6. Close the compartment door
7. Scramble the combination dials to lock
the door and conceal your combination (A)
8. Close the shutter door (B)
Reminder:
(A) The release button will open the lock
until you scramble the dials
(B) Keep the shutter door closed to increase
weather resistance and to conceal the
dials from view

https://www.sentrysafe.com/customerCare/retrieveCombination.aspx