Hi Sara,
I saw that you posted the same details in a different thread. I deleted those other posts so we can keep our correspondence here in this one thread which makes it easier to keep track of all the information you share with m.
What you are describing here is nothing I have run into before either in my testing or with a customer. So far as I'm aware, this should not be possible. If you entered your password using your iPhone's keyboard, mSecure was able to sign in to your account, and the data in the app has been decrypted. So that password is most certainly correct. All that happens when you turn on Face ID is that the password you enter is handed over to iOS, it's encrypted by iOS and then stored in the device's "Secure Enclave." That makes it able to be retrieved using Face ID in the future.
Since I have never experienced this issue before, please confirm for me that when you enter your password via your device's keyboard that mSecure is accepting it. I know that sounds strange, but just bear with me because I do not understand what's happening.
Also, do you happen to have another device, any type of device like a PC or Mac but another iOS or Android device would work too, that you can install mSecure on?
Sara