1st check to see if the seat switch sensor is working.. Did you use the clutch? If not try that, if it works then the seat switch could be the problem.

I've seen that happen more than once.  Couple of safely features to make the tractor not Kill someone by making sure their is a butt in the seat.

Have had 2 similar issues but there were codes both times.

One issue it would not come out of park the other it would come out of park but not go into any gear.

I was not very happy about either situation as this was on a pretty low houred tractor.All part of this electronic shift/control switch garbage that is far from durable in my opinion.  Give me an old fashioned lever that does the actual job.

One was a pressure sensor which was pretty easy to change located near battery box. The other was the actual shift controller board in the armrest. Has dinky little magnets that senses the shifter position.  Some sort of board malfunction required replacement. Used to be a reman board but now you get to buy a new one ($600 range) that requires recalibration. New board did not appear to be any different or more robust and offered little to no protection from dirt and dust and actually appeared more open to contaminates than the original.

Both pieces solved the issues but I thought both were less than stellar in durability and life.

Don't take my complaint wrongly.

I think the transmission is plenty durable and I was relieved my issues were not more serious internal issues.

Just did not think a pressure sensor and controller card should have puked with less than 1500 hours on them. To me that does not inspire reliability or durability in these delicate high dollar electronic components and for sure does not make me feel confident about their longevity over the long haul.