When you have it jacked up tires should turn in opposite direction.
About how many hrs on mower and when did you last change drive belt ?
Make sure your belt hasn't jumped off engine and transaxle pulley, or any of the idler pulley's.
Make sure connection for release rod is hooked to transaxle, and forward and reverse is attached.
With release pulled out it should move.
While jacked up start mower and try to run it in forward and reverse.
You can try purging by pulling release start and move to full forward for 5 seconds then full reverse 5 seconds, do this 4 or 5 times then take out Jack push release back in to drive position and try driving it.
Let us know what you find after this.
Thank you for your response, It only has about 600 hours on it. After watching some videos on youtube, I went out today and decided start checking things on the under side from front to back. I started pushing and pulling on anything that would move..starting with the drive belt..it seemed to have normal tension on it and all hardware seemed ok. I didn't suspect that anyway, because the transmission would TRY to move and it made a whining noise and no belt slipping smell or anything. Next, I checked the brake disk, and as I suspected, it was free, because like I mentioned, when jacked up,, the tires would turn. Only when it was on the ground, they seemed locked up. After checking all the linkages and cables, I manually moved the lever linkage on the hydrostat release rod, and it felt like it moved slightly towards the front of the mower. The rod with the spring on it,towards the rear of the mower didn't move at all. As I reached to spring from the front of the rear tire, I noticed the tire moved slightly and the other tire was leaning on the floor. The mower was leaning to that side while still on the jack. So, I turned the wheel by hand and it turned freely..both forward and backwards with the other wheel sitting on the ground. So I let it down off the jack and started the mower up, it worked Perfect, both directions.. I mowed my lawn with it and it still is running fine. The only thing I know that could of corrected it was that the linkage must of not been all the way forward... but.. why was it locked up though.. I still should of been able to push the mower forward or backwards by hand if that was the case. I am still puzzled... but.. it's WORKING... I'm still puzzled about it all..but glad I didn't have to go out an buy another mower.
On the Purging you were talking about, do you do it with the release out? I was under the impression that you should never try to operate the transmission with that lever out, because it could cause damage, and it's only for towing or pushing the mower by hand.