My guess is that somehow authn support is not enabled in the user's browser. I manually disabled authn in Firefox and I was able to get the same experience as the user.
To disable Authn:
Open Firefox and type about:config in the address bar.
Search for security.webauth.webauthn and set it to false by double-clicking it. This will disable the WebAuthn API.
I have done a two-way solution:
Disable fingerprint login if Authn is not supported by the browser
In case of an error during fingerprint login set up, uncheck the toggle and show a snack message.
Fixing #3453.
My guess is that somehow authn support is not enabled in the user's browser. I manually disabled authn in Firefox and I was able to get the same experience as the user.
To disable Authn:
I have done a two-way solution: