Drobo Gen 2 Not Mounting on Mac Pro Late 2013 Mac OS Big Sur

After Mac OS Big Sur Update, my Drobo Gen 2 is not mounting. The Drobo Dashboard (version 3.5.2) recognizes the Drobo and everything is green. The firmware on Drobo is version 1.4.2. The Drobo is connected to Mac via FireWire cable. I have also tried USB 2.0 cable and connected directly to Mac. It does not work. The disk utility shows Drobo, and when I run “first aid” on the disk utility, the following error message results:

Performing fsck_hfs -fy -x /dev/rdisk3s2
Checking Journaled HFS Plus volume.
Invalid B-tree node size
The volume Drobo could not be verified completely.
File system check exit code is 8.
Restoring the original state found as unmounted.
File system verify or repair failed. : (-69845)