We have submitted FB21575784 about it.

@potterdai2 we've had this entitlement active in our app for over a year now. We’ve noticed the passkeys stopped working on macOS 15.4.1 while they work fine on 15.3.2 with the same app build. This may indicate a regression introduced in macOS 15.4. Are you testing with 15.4? Can you check with an older macOS version?