Hi!

If it's not engaging in the recording mode, have you checked to be
sure the record prevention safety switch is doing its job?

There should be a small arm that senses whether or not the erase-
protection tabs have been removed from the cassette. If the switch or
optical sensor attached to this arm aren't working, the deck will
refuse to record on a tape.

If it's a switch, you could try shorting across it temporarily and
attempting to engage the recording mode. For a full logic deck like
the one you have, you will need to have a tape in place for it to work
properly--otherwise the tape spill sensor may well shut it down if it
starts in the first place. (Most won't operate without a tape in
place.)

William