If it’s in a restricted state, then try doing a Function 21 from the front panel of the system. You have to be in Manual mode to do this.
Select manual mode, then push the increment (↑) or decrement (↓) button on the control panel until 21 appears in the Function/Data display. Press the Enter button on the control panel.
Once you are in there, you can do an option 14 to end Batch Restricted mode. This will start the controlling subsystem and you can get back into the system. In my tests, the console was also varied back on, but if not in your case, then at least QINTER and TCP/IP will have been restarted and you can log in from another terminal at that point.