You tried logging into your mail.com account and filled in the correct login data, but the login failed anyway?
Older versions of the mail.com Mail App are not longer supported by mail.com for security reasons. It is recommended that you update your mobile device in order to be able to use all mail.com apps in the future.
There are different conditions that cause your account to be locked by the system. Some of these do not show an error message in the mobile view.
It could be that a technical problem at mail.com has prevented you from signing in.