2004 TRX 400 Rancher won’t go into gear

Hey all. It seems a lot of people have posted about ESP issues and flashing dashed lines, but on the gear display, but my issue seems slightly different. I bought the ATV a month ago and the only issues I had were a dead battery and it wouldn’t idle without a slight pull of the choke. The ATV wasn’t used much spending a majority of its time in an older gentleman’s garage collecting dust with only 100 hrs on it. Last week I was having a difficult time getting into reverse using the manual handle on the left side of the vehicle. Even though the handle was moved to the R position it would remain in neutral (with no dashed on the display just N). Today I changed the battery and was going to move it into the garage to change the oil and clean the carb. It started fine after the battery install. But when I went from neutral to drive (in AUTO), it displayed drive but didn’t move when i depressed the throttle. The engine revs fine, but wheeler moves freely when pushed with (drive displayed). I have to go all the way to reverse (some times) with the handle to get N to display. This makes me think it’s the mechanical shift cable. I know it is irrelevant, but when in ESP drive the electric shifter moter can be heard when I depress up or down and I get the proper gear displayed. However the wheeler still won’t go into gear and seemingly remains in neutral even though it displays in gear or drive. I took off the fender and it appears the cable from the handle is working (may be a bit sluggish however). I’m not hearing any grinding noises from the transmission. In fact I’m not hearing any transmission noises when I go from N to D (no clicks, movement, nothing 😕). I am some what mechanically inclinde, but no little about ATVs. Especially these new electronic shift Hondas. Any thoughts??