Last night:
Three drives that work fine on my 2016 MBP (on Monterey: too old to upgrade) are not mounting on my New MBA M2 Sequoia. Two Lacie disks ask permission then don't mount. Lacie 8TB asks permission repeatedly but does not mount. Both Lacie drives are several years old. A Seagate just spins for a while with no recognition. Lacie: 8TB powered HDD and 2TB rugged non-powered HDD; Seagate 2TB pocket HDD.
I used MBP to copy drive to drive. I had problems copying data over from one drive to another bc of old format (wrong format. Reformatted on MBP those drives with problems). All are now APFS case sensitive (to accept old files with case sensitive files). All drives, regardless of age or format, mount with no issues on my MBP Monterey.
Today:
Lacie rugged 2TB mounts in Finder and in DU and identifies as APFS. First Aid runs. Unmounting in Finder does not unmount in DU. Formatted on MBA to APFS case sensitive to see whether that fixes the APFS/Mac Journaled weirdness. As it formats the drive, DU says it's formatting to Mac Journaled. When format is done, DU then identifies the drive as APFS. Lacie 8TB still asks permission over and over and does not mount in DU or in FInder. Seagate unchanged--then tried again; see below.
All problem drives continue to mount without issue on MBP Monterey. Seagate also formats on MBP as Mac Journaled then reports as APFS.
Final state: 2 TB Lacie Rugged works. 8TB Lacie powered asks permission but does not mount in DU or Finder. Seagate now mounts without difficulty--I discovered that the USB cable was not pushed fully in. When formatting the Seagate yet again as APFS on MBA, DU reports it is formatting it as Mac Journaled. When format is complete, DU reports it as APFS.
All drives were plugged every time directly into both MBP and MBA. Seagate uses a USB A to USB C adapter. All others are USB C. Somewhere in this mess I followed Apple support instructions to upgrade from Sonoma to Sequoia. But whatever problems I was having on Sequoia happened on Sonoma as well.
Clearly Drive age is a factor. Both the 8TB and 2TB Lacie drives are at least five years old. Seagate is probably older. Power also a factor as the Seagate that mounted in MBP but did not in MBA was only half plugged in at the drive end. When fully plugged in, it mounted immediately.
I'd like to have all of them work, since they do actually work, just not with this MBA on Sequoia. The 8TB is my TM drive. Having just spent over $1k on a MBA, I don't want to buy a new desk drive as well.