New canister filter not keeping tank clear. Why?

Have you checked the impeller. It sounds like the impeller is broken. The motor will sound like its working, but not pick up water.

Motor is working too hard because filters are blocked.

The canister has a filter as well. It needs to be replaced or cleaned. A damaged canister filter will feed dirt into the HEPA filter. (and the motor)
An improperly installed filter can allow dirt to bypass the canister filter and collect in the HEPA filter.
I suggest a new canister filter and then clean it carefully every week.
Here is a list of the filters for your vacuum.

I love the Dyson (DC07), but after 7 or 8 years it lost suction and needed some attention beyond filter cleaning. After much online research I found the few bits of advice that for me were the holy grail. After all of the standard stuff, clear clogs, clean filters etc..... In this order: 1) Remove & empty the canister, ***important****-leave the canister bottom lid open. 2) remove the three star screws at the top of the canister. It'll take a bit of pressure to pull the top up, there's a rubber seal. When you pull it up there will be a rod running down into the canister, leave it be, just pull up the top high enough to clear out any debris. 3) Put the top back on aligning the screws, when you lower it make sure the bottom of the rod engages with the hole at the bottom center of the canister, this is why you left the bottom lid open. Put the three star screws back in. 4) Turn the canister upside down, lid open, and keeping in mind this is thin plastic, gently tug upwards on the four fins that surround the bottom rubber seal. This part is held in by friction, so work your way around the four fins gently pulling until you work the ring they're connected to free. This will give you access to the inside of the canister. 5) remove the round perforated section by tugging upwards on it, set it aside with the fin part. 6) Take the canister to a laundry tub or large sink and holding it bottom up fill it with hot/warm water. Grasping the center section shake it vigorously and turn it upside down while shaking and a bunch of sh*t will come out. Repeat several times. 7) Dry thoroughly, you might use a hairdryer held to the center tube, but only if you can switch off the heat and use air only. Make sure its 200% dry, water will kill your machine 8) clean and replace the round perforated section 9) replace the fin section, I'd suggest pulling the round rubber part off of the fin part and setting it in place on the canister first, then follow with the plastic fin part. If you don't do it this way the rubber won't seat properly and the bottom lid won't close. 10) Close the lid, replace the canister, and staaaaaart suckin like it's brand new.

you should check the round filter casing on theleft and the right side of machine to make sure they are snaped in right also the clear hose on the bottom sumtimes comes unhooked.

If the usual clog clearing and filter cleaning doesn;t work-> I love the Dyson (DC07), but after 7 or 8 years it lost suction and needed some attention beyond filter cleaning. After much online research I found the few bits of advice that for me were the holy grail. After all of the standard stuff, clear clogs, clean filters etc..... In this order: 1) Remove & empty the canister, ***important****-leave the canister bottom lid open. 2) remove the three star screws at the top of the canister. It'll take a bit of pressure to pull the top up, there's a rubber seal. When you pull it up there will be a rod running down into the canister, leave it be, just pull up the top high enough to clear out any debris. 3) Put the top back on aligning the screws, when you lower it make sure the bottom of the rod engages with the hole at the bottom center of the canister, this is why you left the bottom lid open. Put the three star screws back in. 4) Turn the canister upside down, lid open, and keeping in mind this is thin plastic, gently tug upwards on the four fins that surround the bottom rubber seal. This part is held in by friction, so work your way around the four fins gently pulling until you work the ring they're connected to free. This will give you access to the inside of the canister. 5) remove the round perforated section by tugging upwards on it, set it aside with the fin part. 6) Take the canister to a laundry tub or large sink and holding it bottom up fill it with hot/warm water. Grasping the center section shake it vigorously and turn it upside down while shaking and a bunch of sh*t will come out. Repeat several times. 7) Dry thoroughly, you might use a hairdryer held to the center tube, but only if you can switch off the heat and use air only. Make sure its 200% dry, water will kill your machine 8) clean and replace the round perforated section 9) replace the fin section, I'd suggest pulling the round rubber part off of the fin part and setting it in place on the canister first, then follow with the plastic fin part. If you don't do it this way the rubber won't seat properly and the bottom lid won't close. 10) Close the lid, replace the canister, and staaaaaart suckin like it's brand new.

I love the Dyson (DC07), but after 7 or 8 years it lost suction and needed some attention beyond filter cleaning. After much online research I found the few bits of advice that for me were the holy grail. After all of the standard stuff, clear clogs, clean filters etc..... In this order: 1) Remove & empty the canister, ***important****-leave the canister bottom lid open. 2) remove the three star screws at the top of the canister. It'll take a bit of pressure to pull the top up, there's a rubber seal. When you pull it up there will be a rod running down into the canister, leave it be, just pull up the top high enough to clear out any debris. 3) Put the top back on aligning the screws, when you lower it make sure the bottom of the rod engages with the hole at the bottom center of the canister, this is why you left the bottom lid open. Put the three star screws back in. 4) Turn the canister upside down, lid open, and keeping in mind this is thin plastic, gently tug upwards on the four fins that surround the bottom rubber seal. This part is held in by friction, so work your way around the four fins gently pulling until you work the ring they're connected to free. This will give you access to the inside of the canister. 5) remove the round perforated section by tugging upwards on it, set it aside with the fin part. 6) Take the canister to a laundry tub or large sink and holding it bottom up fill it with hot/warm water. Grasping the center section shake it vigorously and turn it upside down while shaking and a bunch of sh*t will come out. Repeat several times. 7) Dry thoroughly, you might use a hairdryer held to the center tube, but only if you can switch off the heat and use air only. Make sure its 200% dry, water will kill your machine 8) clean and replace the round perforated section 9) replace the fin section, I'd suggest pulling the round rubber part off of the fin part and setting it in place on the canister first, then follow with the plastic fin part. If you don't do it this way the rubber won't seat properly and the bottom lid won't close. 10) Close the lid, replace the canister, and staaaaaart suckin like it's brand new.

At the top of your wand, do you have a plastic swivel that cover a hole in the wand? This is for when you are cleaning curtains, and if that is open, or cracked you will loose suction there... also check your hose for cracks, or breaks. If it were in the shop I would put a gauge on it... normal suction is about 80-95 inches of water lift at the end of the hose. Once you have check each section of the hose, and wand, check the housing for cracks, a missing gasket (Very Good Reason For Lack Of Suction) As to your Filter, how long have you used that one filter, you can clean them for a while, but once a paper filter gets full of FINE dust you won't get it all out, you will have to replace the filter itself at that point. I hope this was helpful.

if the blower is much stronger than the suction, you may have an air leakwhere the cover fits on tank or possibly a warped tank or cover. feel all around the unit for air being drawn in somewhere besides the hose. try it without the hose on and block the inlet for a couple seconds to see if the unit leaks air in. also replace the filter , dont try to clean it, the pores clog and reduce suction and damage motor.

There is an area on the back of the tank where you will see lines, put your thumb there and pull the top half of the tank towards yourself. That should open the machine so you can replace your after filter.