Re: Right cable, wrong hole.
Several bits of kit from around mid 80`s seemed to share a common chassis design with a filtered IEC fixed plug, and a resettable circuit breaker just above. The standard metalwork had a recess above the breaker tit that was about 0.5mm less wide than an IEC cable socket and a similar depth. Usually bottom corner RHS from the front, and you could plug the power in blind from the front, unless you squeezed it into that nice space above the breaker, the only giveaway was that it was moveable vertically while seemingly happily retained.
A number of experienced chaps fell in this trap without going round the back and going "Dohhh!!!".
I did too, Once only.
If you poke it in and it feels.....different, time to think very carefully, IMHO.