Sounds like something is jammed or stuck in the controls under the seat.
First, remove the round inspection cover on the right side. There will be 2 levers from above that are in contact with the front of a roller lever. If the levers are not in contact with the roller, the valve is stuck. Move the roller back and forth and see if it will free up. It should be spring loaded forward against the levers.
You can push the roller to the side and move it in front of the levers. Start the engine and see if the arms stay down.
!!Be careful reaching in there! Moving parts inside!!
Then carefully push back on the roller, the arms should go up. If they do, the problem is above in the position control assembly.
The most common problem with the position control lever is rust. Check the rubber boot around the upper link, if it's rotted away there will be rusty scale on everything and water entering the transmission. Typically the upper cover can be removed, the linkage cleaned and lubed and adjusted. You will need a service manual though.