Transmission stuck in 4X4

Newbie has a 07 RTV 900 that was sitting in a damp environment for several years not used. I changed all fluids & filters right away. With difficulty put it in 4wd and can not get back to 2wd. I've removed the cable at the trany and cable/ linkage is free. I'm an old farm boy good with a wrench. Help Please! I can not move the lever on the tranny where the cable connects.
Thanks
Dan in the U.P.

Shaft might be seized where it enters the case. Keep apply penetrating oil and driving.

Give it time and a good run to heat up the cases it may just leg go.

A little backing up and going forward helps to release 4wd as the pressure on the gearing keeps it in gear.