Always check for termination, and then the cable first.

But a hard drive that over 20 years old can have other issues as well. Leaking caps for one, the head sticking is another. If you tap it on the side with a hammer (lightly) you can free up the head for now, but it will stick again. Some other members seem to know what to do to fix this. But at this day and age for a 20 year old drive, it's time for a new drive, even if it is solid state.