Is this a legacy product now that WD have done something with My Discovery? I bought it last year as a backup device for OS 10.15.7 (Catalina using Time Machine), but it is no longer being recognised as a backup device.
Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting:
Many thanks Keerti
Time Machine /Passport answered my question this morning. It took in the region of 36 hours to do a first back-up of 270 GB after a complete re-initialise . Seems a bit excessive to me but, if it is working again for the time being, it gives me breathing space to find a more robust solution.