Hardware key PIN does not work on registration

I am trying to set up 2FA using hardware keys, but I get stalled on this cycle:

1. Select “Add hardware key”
2. 1Password helpfully intercepts, I escape or click the hardware key icon
3. System asks for PIN. I put in the hardware key PIN.
4. System says to reinsert and activate. I do so.
5. System says incorrect PIN.

Any thoughts? I’ve been using Safari / Mac but I can’t imagine browser matters.