This answer is valid for IDEA StatiCa version 21.1. and older versions
This error message means the inputted credentials are wrong.
In most cases, the password is wrong for some reason. First, check if typed in correctly.
If you have lost your password, go to https://my.ideastatica.com/account/forgot-password, input your User name and you will get the password recovery mail to your email address.
In case you are not sure about your User name, please contact your license administrator, or in case of a free license, contact our support team.