Same problem here: different SSDs (SanDisk Extreme Pro, Samsung T7, very new Crucial portable 4 TB) + APFS encrypted work
+ fine at my MacBook Pro (M1, Big Sur), but
- are visible but can not be decrypted at the iPad Pro.
After submitting the password the same pop up asking for the password again.
I tried all different combinations (different passwords, cables, adapters even different partitions on the ssds) even second iPad or two other macs for new APFS encryption. Same bad results.
What's the problem here (I searched for hours and just found this only one actual thread here. It seems that nobody out there is having these issues, except for us here ;).
I really hope to get it working, especially because of Apples announcements that exactly this should work fine not only with Macs but with iPadOS 14, too.
Any help or good advice is so welcome.