I work at a Deere dealership. Did you lubricate the spring-loaded half moon key? The most common issue is that those keys arent lubricated every year. (I usually lube mine at the beginning and then again halfway thru the season)
Once you lubricate the keys on each end of the axle, you should be able to hear them "click" when you rotate the wheel FORWARD by hand. If you rotate the wheel in REVERSE, it should turn the axle shaft.
If one side isnt clicking, then there is an issue. If they do click, but it still hangs up on the left side, there may be an issue in the transmission not releasing the drive.
*The gears can also be flipped and installed backward. If that happened, the wheel will click when rotated in REVERSE, and turn the axle when rotated FORWARD. *
I did have one customer replace the spring loaded key with a solid key with no spring. Needless to say, his drive wheels would never release. Good luck and hope this helps!