I have an external drive which has always worked fine - until today. The drive won't show up in finder. It shows in Disk Utility but won't open (it's greyed out on the left hand side). I tried "First Aid" but after an hour of nothing happening, restarted my Mac. The external drive is vibrating and the light is on. I've tried different USB ports, a different cable and a different Mac (both Macs are up to date). Any advice?!