After the last update to 1.52.0 of the Firefox add in version of Bitwarden and 1.52.1 version for Chrome, it will no longer match an IPv6 IP address for autofill. The URI is an IPv6 IP address, not a TLD and it worked up until this latest update.
It looks like the Bitwarden team is aware of the issue. It seems to be causing a few unexpected issues.
Having the same problem at the moment, so perhaps not fixed yet? Adding DNS that resolves to IPv6 is fine, but not when adding IPv6 addresses themselves to the secret.