Weekly tech discussion and tech support thread
Weekly tech discussion and tech support thread
In desperation I’d first try (if you haven’t already) all the different usb ports in case it’s a faulty port. Then a different USB cable, assuming it’s not built into the case. If it has some external power supply I’d try a different one if possible.
Beyond that, by “very old” do you mean spinning rust, or are they SSD?
Either way, there’s always a way to get into the case, if it’s a popular enough drive/case, there may be a video on how to do it. Depending on they type of drive there maybe more you can check on the inside.