Toro Groundmaster 328D, won't move Forward or Reverse

[sparky75087]

One day I was mowing a bit of some Tallerr grass maybe about a foot tall and I was cutting slowly but surely and out of nowhere it stopped moving, after pushing pedal in reverse and forward a couple times it still wouldn't move at all. just trying to see if anyone has any idea what could have happened to it that causes it not to track forward or in reverse? I searched online for these drawings but don't necessarily know how to make sense of them can somebody help explain to me how the traction system works and possible root cause of issue. Any help is appreciated.

 

[Xfaxman]

Check the hydraulic oil filter at the input to the transaxle.
If it is sucking air the machine will not move.

Guess how I know that.