Thank you for contacting us, and I'm really sorry for the problem you are experiencing here. Unfortunately, there is not a lot we can do in these situations. The authentication information for mSecure is only stored in the device's secure memory location and in your memory in the form of your master password used for unlocking the app. I'm not sure what happened when you upgraded iOS, but if the Face ID information was altered in some way, the authentication data in the device's secure storage is completely wiped out which causes Face/Touch ID to be disabled for mSecure.
Also, in order for the information stored in mSecure to be as secure as possible, mSeven Software doesn't acquire our customer's password or the information stored in their mSecure account, so there is no way for us to retrieve either of those items. In order to keep your information from being accessed without your permission, it is not possible to bypass or change an account's password when mSecure is not accepting the password the user is entering.
Do you happen to have access to mSecure on any device, or were you only using it on your iPhone?
It's great to hear you were able to figure out your password Ferdinand! We are planning on adding a password reminder feature to mSecure in the future. It's already planned for a 6.x release. It will work by asking you for your password, but if you are not able to remember it, it will allow you to unlock the app using your Face/Fingerprint. After it's unlocked, if you weren't able to unlock using your password, you will then be able to change your password right away. So far as I'm aware, it will still be up to the user to make sure the password is changed, but something will happen to bring the issue to the forefront hopefully before it's a huge problem.
When you mention not knowing how to sync your current iOS 14.4 Face ID for mSecure, can you explain that in more detail? Are you trying to set up Face ID unlock in mSecure again not that you're back into the app?