Big shot in the dark, is there any possibility your battery
polarity connections are reversed?
Years ago (before the early 1960's) when cars had generators instead of alternators, I did car radio
repair. Radios had just become partly solid state. Every once in a while, I'd run across someone whose radio
had quit, but everything in the car worked correctly.
The radio worked fine on the bench.
In each case, the car battery
had gotten installed backwards for various reasons.
The only thing polarity sensitive in the whole car was the radio !