Troybilt Pony w a B&S 500cc 17.5 HP engine. Will not move while in neutral.

The Pony is a CVT model. I jacked up the back of the mower and no matter whether it is in D N or P, one wheel turns in one direction while the other rotates in the other direction. The wheels do turn freely while it is jacked up. I am trying to push the mower manually while in neutral, but it will not move due to the wheels moving in opposite directions. The shift lever is attached to a "rod" link (or "rods" linkages, I don't recall exactly) that lead to the "shift mechanism" on the transmission/differential. That appears to be functioning properly and the "shift mechanism" at the transmission moves back and forth (I'm guessing it is functioning as designed, but I am not sure)...in other words it appears to be shifting from D to N to R.

Does anyone know how I can try and troubleshoot the issue? so I can move the riding mower by pushing it?

thank you very much

PS, I can't start the engine right now because the carburetor is leaking.

The brake is jambed on which locks the diff thus the wheels turn in different direction.
So off with the rea wheel then off with the brake & free it up.
The brake caliper has 3 bolts, do not touch the middle one, it adjusts the brake.
Take lots of photos particularly of how the brake spring attaches .
The lever pushes on 2 pins which push on a very thin plate which pushed the puck into the disc.
There is a second puck behind the disc. The pins, pucks & shim plate may fall out when you remove the caliper so put some thin underneth to catch them.
Usually you get debris build up which holds moisture which causes the pins to corrode .
Occasionally a stick will jamb the brake lever.