Nachi AT20 controller safety bypass

I'm guessing you mean the AX20 controller?

The safety signals to and from the controller are on TBEX1 and TBEX2 connectors.

See attached installation manual safety signals section.

If you take that robot from Toyota factory, it's mean this controller has a Toyota spec.
But you can't find TBEX1 or TBEX2 socket on that controller.
Because Toyota spec. is different.

I never used AT controller before, but it can be similar with AW.
You should check X-LINE socket.
This socket using for safety connections.

Also we are using jumper for this socket. (But controller spec is different. You should be carefull)
Please check attached picture for referance.