Error Message: "The disk you inserted was not readable by this computer."

You may have a hardware issue with the WD drive or its cable. Another possibility is the USB-C port on your laptop has worn down so now the connection is much looser which is causing a disconnect of the WD drive which then corrupted the file system on the WD drive.

First thing I would do is check the health of the WD drive by running DriveDx (free trial period). You will need to install a special USB driver in order to attempt to access the health information on the external drive. Post the complete DriveDx text report here using the "Additional Text" icon which looks like a piece of paper so I can examine the report.

Does it appear in Disk Utility, and if so, does ** prompt you to initialize it?

Disk Utility User Guide for Mac - Apple Support

Don't erase it, just write back with what you determine.

FYI if you installed any Western Digital drive "manager" or similarly categorized utility, uninstall it. Those things have been known to corrupt perfectly good hard disk drives.