When logging into the app for the first time, you create a free account linked to your email address, a six-digit code is sent to your email to log into the app.
Periodically, the app requests you to log in again, and a new code will be sent to your email address, this is done to protect your data that you register in the app.
Did you not receive the login code? Please check that you entered the correct email address and also check your spam folder