The auto trans light came on and now the gearbox is locke...

Hello and welcome

Hey was going on

This means the transmission is going into failsafe mode. transmission failsafe occurs when the transmission senses a fault or is missing a needed input that is required for proper operation. Transmission failsafe can occur for many, many reasons. Anything from a simple low fluid level or failed sensor to complete transmission failure can cause failsafe. Even a missing input from the ABS system or a faulty alternator can cause failsafe, etc, etc, etc.The good news is that when failsafe occurs, the transmission computer logs a record of the fault, which can be read out to shed additional light on the exact nature of the issue. Thus, the only way to determine why the transmission is in failsafe is to have the fault memory read out using a compatible scan tool. Once the fault memory is read, the problem can be identified, and the issue fixed.Without knowing what faults are stored, all a person can do is guess at the problem - which can get very expensive, very quickly.

what is the best thing to do at this point

You need to get it scanned. That’s the only next step

Okay

Good luck with your car