Record button won’t press? (Technics RS-T18)

Recently picked up an old Technics component deck from a thrift store. It works well for playback after I bought some adapters. The trouble is when I try to record. The button simply won’t press down. Tried side A and B, same result. Looked for anti-record tabs on the tape and didn’t see any. Is it a tape problem or a deck problem? It’s the only blank tape I have so I’d prefer to be sure before recording on a different tape.