It's something to do with
Oct 31 19:45:10 unRAID kernel: Buffer I/O error on dev md23, logical block 4, async page read
Oct 31 19:45:10 unRAID kernel: Buffer I/O error on dev md23, logical block 8, async page read
Oct 31 19:45:10 unRAID kernel: Buffer I/O error on dev md23, logical block 16, async page read
this that happens before the system tries to mount disk 23
I'm guessing that you're running into this issue:
Since disk 23 is a new disk and the system has to clear it. If you downgrade to 6.7.2, it'll clear it in the background and your shares will be available.