private relay email does not exist

I have previously setup a private relay email as part of a Sign in with Apple process.

I was expecting some emails on that address and they never arrived. I tested the address by sending it an email, and received an error indicating that no such address exists.

I have never cancelled this address and can still see it setup in my "Hide my email" settings.

How can I get this email address working again? How can I be sure that other private relay emails I have setup do not have the same problem?