Coil nailer driver will not retract only if you push up by hand

Reasons for driver not retracting./
Check band on the outer part of the cylinder missing or not in place. Pull out cylinder and look for series of holes. These holes should be covered with rubber band or oring. The band/oring should fit snuggly.
Driver slightly bent making it hard to push driver up. Push driver up with any tool that fits into the nose. Should move up rather easily. If hard, pull driver and check for damage or oring too tight/loose.
Too much air leaking past the nose due to worn lower bumper. Bumper should not have cracks or missing pieces. Some nailers use a second seal below the bumper made of metal or vinyl. If broken or missing, replace. Finally, piston will not retract of there is an obstruction in the headvalve exhaust port. Good luck

The feeder piston should be very hard to retract by hand and should move back and forth as quickly as driver piston moves. With nails removed and side door open, activate gun on rubber surface (old coiled up air hose or water hose ) and make sure driver and feeder move quickly. If not check for debris within feed piston or air passage to feedpiston. The spring straddles the feeder with the slightly bent part of the spring arms contacting the upper surface of the feeder (little grooves cut into feeder). When installed correctly, the tip of the spring arms will be pointing upwards and the back part of the spring between the two loops will be contacting the feeder shaft. Good luck.

Driver not retracting is caused by bent shaft, oring too tight/loose, check seal missing, or lower bumper cracked/missing pieces. With air hose removed, push driver all the way up with thin metal. Should be rather easy to move. If hard to push, remove head and pull driver to check for items mentioned above. If easy to push up, test gun. If driver stays all the way down, pull cylinder and make sure check seal is in place. If driver goes partially up, oring too tight/loose, lube piston seal with white grease or silicone paste and retest (if bent, adjust or replace). Good luck

The driver will not retract if it is bent or if the checkseal on the outer part of cylinder is broken. Remove head and examine driver. Repair or replace as needed. If driver is ok, pull cylinder and examine rubber checkseal. It should be installed snugly around series of holes on outside of cylinder. If checkseal fits loose or broken you can use a series of orings to fill space(about 3 to 4 orings). Good luck

Causes of piston not retracting are as follows. Cracked /worn bumper, if cracked air will leak between piston and bumper. Try test, remove nails and dry fire gun against rubber or soft wood; depress trigger push gun against wood/rubber and hold in this position. Piston should stay down and no air should leak past nose. Worn piston oring, piston should not slide down cylinder under its own weight. Loose or missing check seal, remove cylinder and look for black rubber band around series of holes. Band should be in place and fit snuggly. Good luck

if its new warranty it,
otherwise all it should need is a rebuild kit . its just a bunch of orings and gaskets. pretty easy to do. take some pictures as you take it apart to help with reassembly.
Dewalt should have scematics online or ereplacements.com

First does it retract after unplugging the air and if so I would look at the trigger valve assembly for a sticking plunger. If not then I would look at the firing valve in the cap. Let me know if I can help further.

Your nailer shares design features with Milwaukee and Ridgid. All three brands experience the same issue. Lets go thru a series of simple tests to determine the problem. First and most simple test, manually load the nails and fire the gun untill miss-fire. Upon mis-fire disconnect air, open latch and check if the driver is all the way up into the cylinder or is partially down blocking next nail. If driver is down blocking next nail, replace the driver oring and retest. If driver is up all the way, remove nails, reconnect airline, leave latch open and fire gun against rubber (old tire or coiled up waterhose/airhose) this time holding the gun down and keeping the trigger depressed. In this position, the driver will remain down and feeder will remain retracted. With feeder retracted and screwdriver in hand carefully check the spring tension on the feeder (should be rather firm tension on spring and the feeder must retract with good force). If no tension or weak, replace feed spring. When you finally release the trigger, the driver will retract and the feeder should return with good force. If feeder does not return with force, replace orings and spring behind feed piston. If all tests are ok, remove head, check lower bumper in gun for cracks or missing pieces. Replace as necessary. Lube all orings with silicone lube available at Lowes in the plumbing department. (Danco brand) Good luck on your repair and email your questions.

There is a spring that is broken or the joint just needs some lubricant that can help take care of this issue

There is a number of reasons that this will happen. Is the driver (plunger) physically stuck? Take a small screw driver and see if it can manually be pushed back. It may also be a broken head valve spring, or a stuck head valve (you have to remove the rear cap to get to these parts) Maybe this unit just needs an O-ring kit. Try these things and let me know