https://support.msecure.com/en/support/solutions/articles/36000064484-msecure-accounts-explained

Hi everyone,

A username is an email address. I believe your issue is that you don't have an account with us. mSecure 5 is the first and only version of our app to use an account system. All previous versions had you create a device specific unlock password. This unlock password is not an account. Please create an account in order to get started with mSecure 5.