Bottom wheel of garage door came off track

If you're having to hold that inside button down to bring it down that is because of your sensors being out of alignment. On the bottom left and bottom right of your garage door track are your photo eyes and if they're not cleaned and pointing toward each other, then they will not allow the door to close. It will only close with the inside button because it is hardwired and when you hold the button down it shoots a continuous current that bypasses Those sensors. Remotes and keypad are wireless and must have photo sensors aligned to work

You need to adjust the wheels up with the adjustment screws on the bottom end of the door. The door will lift slightly enough to let the wheels and door clear the track. So up and in. Then when replacing, lift up and set down on the track on the rollers and adjust up turning screw so that the door rolls easily without rubbing. Some doors adjustment screw is on the bottom door end, some are on the side of the bottom of the door a few inches back, depending on model.

Something could be binding in the track. Try lubricating all the moving parts. Also, the IR sensor at the bottom, which is designed to prevent the door from hitting something, could need to be aimed again. On mine, the IR sending unit at the bottom was burned out. If you have the installation manual, it may have a trouble shooting guide.

The window track should have a bolt at the bottom so the track can be moved away from the window to allow enough room to slip it in between the tracks.Also the door skin can be unbolted to gain access from the outside of the door which may make it easier.

You can buy new wheels at hardware store.
http://www.amazon.com/National-Hardware-V7601-Standard-Rollers/dp/B002KFZU76
Remove the 2 hex nuts that hold the wheel-brace.
Insert new wheel in brace, and then reattach to door with hex nuts
Another thing I used to do is take the big channel locks and squeeze down the track a bit where the wheels come off.

You need to call a door technician. The bottom rollers are usually connected by a cable to the door spring and can be dangerous.

If memory serves, 2 screws on the left edge facing the striker, 2 screws on the front edge facing the headlight, 2 screws on the bottom edge, 1 screw behind the door handle cover, 1 or 2 under the arm rest, and don't forget to remove the quad cover at the front edge of the window so you don't break it taking off the panel.

Looking at the opened door from the inside remove the philips screw near the upper hinge. Pry the speaker grill off with a thin blade putty knife, starting at the bottom left and work to the right. Remove speaker screws and the three screws in the recessed plastic spaces behind. Remove the square covers behind the handle and in the arm rest. Remove the 2 philips screws exposed. Start to pry from the top hinge side between the plastic door panel and the metal door. Work your way around the door until plastic clips release. Once the bottom of the panel and sides are free, lift the panel up and off the door being careful not to pull wiring and door handle mechanism loose. Unplug the as much of the wiring as you can and support the panel so as to not stretch the wiring. Pop the plastic retaining clip on the door handle connecting rod and lift the rod out of the handle. Slowly peel back the vinyl/rubber door cover stuck to the metal door. The window is held in the lower track with two clips that are bolted to the track. Unbolt by raising or lowering the window and using a 10MM socket on the nuts to loosen. Remove the window seal along trhe bottom of the window opening by prying straight up. You can then remove the window and re-epoxy in the lower clips and reassemble window in reverse order.

You probably have a stripped gear. Take the cover off the opener and the bottom will be filled with white shavings and the gear will be missing teeth. You can repair with a liftmaster gear and sprocket kit.

IF THE DOOR CLOSES ALL THE WAY WHEN HOLDING DOWN THE WALL BUTTON AND REVERSES 6" FROM THE FLOOR WHEN NOT HOLDING THE BUTTON.
I WOULD GUESS THAT THE SAFETY EYES ARE MOUNTED ON THE TRACK.
WHEN THE DOOR CLOSES THE TRACK AT THE BOTTOM IS TOO TIGHT CAUSING IT TO FLEX AS THE DOOR GETS NEAR THE BOTTOM. WHEN THE TRACK FLEXES THE EYES ARE POINTING FURTHER AWAY FROM THE DOOR AND EVENTUALLY THEY ARE TOO FAR OUT OF ALINMENT AND THE LED WILL GO OFF - THE DOOR GOES BACK UP.

SOLUTION: YOU CAN USE THE CLAW END OF A HAMMER TO TAP THE TRACK OUT A LITTLE WIDER - TAP NEXT TO THE WALL ON THE BRACKET THAT HOLDS THE TRACK TO THE WALL. MOVE THEM ABOUT 1/4" EACH SIDE.

OR

YOU CAN MOUNT THE BRACKETS TO THE WALL OR THE FLOOR.

THIS SHOULD SOLVE IT

HAVE A GREAT DAY