external hard drive that appears in device manager but not in Windows Explorer

The symptoms seem very similar to those on my external hard drive.

The possible reason is that the meta information on your hard drive could be corrupted. Therefore it is being detected as a drive, but Windows could not find the entry point to access the device.

You can try the disk repair software to repair your disk. But I'm not sure that helps you. I lost 2 of my hard drives for similar reasons.

My suggestion is not to spend time repairing the same thing unless you have very important data that you cannot get more of.

If you want to collect the data, I recommend you go to the company service center. Don't prefer local electronics stores as they could make things worse.

I hope I have been informative enough.