What did Meraki support say? They should have only two answers:
1. It is in fact registered already.
2. It is an issue they can fix
once a few years ago I had an MX that I could not register because Meraki did not have the serial number in their system. I had to wait a few days. I don’t recall if I saw the exact message as you though. It may have said something else in my case.
Let us know what you find out.
- Ex community all-star (⌐⊙_⊙)