It's complaining about an invalid partition:
Feb 6 21:30:19 Atlas emhttpd: /mnt/disk5 mount error: Unsupported partition layout
This shouldn't happen without reason, and according to the output above it's not just the partition that is damages, it's also missing the btrfs superblock, you can try this as a last resort:
btrfs-select-super -s 1 /dev/sdX1
Replace X with correct letter, then see if the recovery options work (it will still be unmountable with Unraid due to the invalid partition)
P.S. also note that most of your other disks are showing previous read errors, and disk2 is lso showing data corruption:
Feb 6 21:30:02 Atlas kernel: BTRFS info (device md1): bdev /dev/md1 errs: wr 0, rd 1815, flush 0, corrupt 0, gen 0
Feb 6 21:30:06 Atlas kernel: BTRFS info (device md2): bdev /dev/md2 errs: wr 0, rd 8155, flush 0, corrupt 1036, gen 0
Feb 6 21:30:12 Atlas kernel: BTRFS info (device md3): bdev /dev/md3 errs: wr 0, rd 15394, flush 0, corrupt 0, gen 0
Feb 6 21:30:15 Atlas kernel: BTRFS info (device md4): bdev /dev/md4 errs: wr 0, rd 19748, flush 0, corrupt 0, gen 0