Welcome to JA my name is Mark.
Essentially this fault code is telling you that the computer failed to recognize that the torque converter was doing what it is supposed to do.
Although the computer requested the converter to operate, nothing happened. Hence, the computer assumes there is a problem with the solenoid that operates the converter and sets the code.
So, you could indeed have a solenoid that is not working anymore or you could have an issue with the torque converter itself. I hope that helps you understand this a bit better. If you need further assistance just reply.
A solenoid is basically an electrical on off switch that controls the flow of transmission fluid.
A torque converter is a fluid coupler that joins the engine to the transmission.
Depending on what you need done, a solenoid repair could run $2-300 whereas a torque converter repair could run $2000.