Can't unlock with PIN on IOS

Hi
On an iPhone SE2, I can enable “unlock with touchid” just fine. However, if I enable “unlock with pin”, bitwarden always asks for my main password instead.

Is this a bug, or am I the problem in this process?

Cheers

Same here. The ‘Use Pin’ option in Settings is also disabled. A user guide would be nice but failing that can anyone else suggest where we’re going wrong?