RZ5424 Right wheel won't operate

Hey guys first time posting on this forum. I've done several searches and I've seen no resolution or fix for this problem. I'm hoping that y'all can help.

the left wheel operates in forward and reverse. The right wheel will not engage. I raised the rear of the mower, Removed the wheels and verified all pullies are spinning.

I followed the steps to purge air from the system After opening the link arm bypass and closing it after the purge.

The transaxle is EZT, RT
Part number is 510375602

This is a sealed unit which I will attempt to repair as a last resort.

I have not attempted to troubleshoot any electrical components yet.

Any help would be awesome!

Check the oil level in the unit. It is not really a sealed unit. It is just called that.

is the r/h bypass stuck in bypass mode , is the input pulley turning the trans pump shaft , , is the pulley stripped ? are the splines ok on the axle output shaft , can you see the swash plate lever-shaft move when you move the control lever? is the brake not stuck on ? and is the unit full of oil ?(oil should be 20w/50 if unit hydro gear ,) from memory oil should be about 2.33 litres give or take a little if all of these things are correct and have been verifed, problem will be internal likely pump piston springs , or check valves in the centre section try downloading a service manual from hydrogear.com entering the model and serial numbers from the transmission
here is web site www.hydro-gear.com/service-and-repair-manuals

take a look hope this helps