USB drive or external disk not showing

The cable, power supply, port or drive may be responsible.

Stop using a drive with unusual noises, read errors or data loss. Do not format, initialise or repair speculatively; seek qualified recovery advice.

If you hear clicking, see repeated read errors or have important unbacked-up data, stop using the drive and seek recovery advice. Do not format, initialise or run repairs.
Without those warning signs, check connections, try a direct USB port without a hub and check the correct power supply for an external disk.
Open File Explorer and select This PC. If the drive appears, first check only whether a familiar folder opens.
If it is still missing, record the model and message for qualified help. Do not accept a Windows formatting prompt if data on the drive must be preserved.

Test after each step and stop when the issue is solved. Checkmarks are not permanently saved.