Something I've seen before is a dependency on the VCR to need a video input to provide a stable "sync" signal for the recording timing. Newer VCRs also have a lockout circuit to prevent operation, except for a black screen and muted audio if no video signal is seen by the VCR input.
I cured that by using a regular video feed from my satellite receiver and then changed the audio input cables over to my radio's output and it worked just fine from there on in.
By using the sat video signal, I tuned to a program guide channel that had a time display ... that made it easy to edit things by having an on-screen clock reference in addition to the time display on the VCR, which can sometimes be hard to read. If you are on cable, they likely have a program guide channel that will do the same.
Hope you're up & running soon, its a great way to obtain excellent quality airchecks, and can be setup to record when you're not at home by using the timer function, just like you were going to record a TV show.
Regards,
Lee