I just upgraded from 1Password 6 to 7. I had 3 vaults, 2 local and 1 in Dropbox.
It seems like the import just pulled in the Dropbox vault and ignored the local ones.
I found this discussion and located the backup local file but I don't see any way in 1Password 7 to import it.
1Password Version: 7.9.3
Extension Version: Not Provided
OS Version: macOS 12.0.1