Your PLC is probably telling the robot other stuff over what ever Network or Hard wired Inputs you have. Maybe you can look at those Output addresses in the PLC find one that is unused and try turning it on (when the machine is not running!!) Then look at your Robot I/O to determine which IN it is.
You could, in a Job that runs every cycle check this Robot IN status and reset the OT based on its status.
So Robot turns on OUT this triggers alarm or whatever. Operator presses Reset which triggers the Robot IN and latches until the Robots OT goes off....I think that would work hard to say without knowing your exact system.