Time Machine prefs for new backup drive stuck on "encrypting"

I do my routine Time Machine backups to an Apple Time Capsule (final generation, 3 TB). They occur right on time.

My internal 1 TB rotating platter hard drive in my 21.5 inch, late 2017 iMac running Catalina macOS 10.15.7 is empty (a year ago I severed the Fusion drive, removed the 28 GB SSD stick from the direct processor slot and replaced it with a 1 TB NVME2 stick from Other World Computing, which I then configured as my boot volume. I erased and reformatted the internal hard drive, which I intended to use as a second Time Machine repository, but I never got 'round to using it until yesterday. I decided (for reasons unknown) to encrypt that backup, but the progress bar hasn't moved in over eighteen hours:

Any idea what I should do?

Thanks so much,

Jim Robertson