The torque convertor can fail but, it is not a common issue. It is more likely you have a stuck neutralizer switch if the transmission is not engaging any direction.
I would remove the floor plate and disconnect the neutralizer solenoid. It is on the top of the transmission and has a green wire and black wire connected to it. A stuck switch in either the transmission handle or loader control handle will energize the solenoid and hold the transmission in neutral. Disconnecting the solenoid will not effect any other function of the transmission.
If that does not help, replace your transmission filter and cut open the old one for inspection. If you find metal in the filter media, then you may have a transmission failure. If you have not serviced this machine properly, it is possible the suction strainer is plugged. You will need to drain all the oil out and then remove the strainer for cleaning.
If you do not find metal in the filter or a plugged strainer, then pressure testing is need to see if the pump has failed or other issue with the transmission control.
If you need more help with this, please post the machine's full serial number with your reply.
I will be away until this evening and can help you further then. If this is not helpful, I will OPT-OUT of the question so, others may help.