Hi @JER
Thanks for your longtime support of Codebook and for posting to the discussion forum, although I’m sorry to hear about the trouble accessing Codebook after adding another Face.
When setting up Codebook to use Face ID, your Codebook Master Password is placed in your Secure Enclave (what stores items accessed with Face ID). When launching Codebook and authenticating via Face ID, this item is retrieved from the Secure Enclave (given the Face ID authentication succeeds) and provided to Codebook.
When adding or removing a Face from your device, the Codebook Master Password item stored in the Secure Enclave is invalidated (i.e. deleted) as a security precaution. Because of this, the only way to regain access to Codebook is to authenticate using your Codebook Master Password, after which you can re-enable Face ID login (which will re-add your Codebook Master Password to the Secure Enclave).
Do you happen to still have access to Codebook on another device (i.e. a Mac that’s using Touch ID)?
I’d recommend trying every combination of password you think you may have used to try to regain access – there’s no limit to the number of passwords you can try (i.e. no lockout after x number of attempts).
There are also a few additional suggestions here: Forgotten Master Passwords
Let me know if any of these suggestions allow you to regain access, and if there’s anything else I can do to assist. Thanks!