Tape out will work even with the unit switched off since it comes directly from the selector switch.
The first thing to check is the push button that selects source or tape. It should be set to source.
It should only be set to tape if you are monitoring a recording with a dedicated playback head or using an external processor that you want to loop back through the pre-amp (e.g. an equalizer).
Do you use any other sources? Do they work?
Regards,
Dean