After several tests, I came to the conclusion that the credentials are not recognized in the following cases:
Since the guide would be too confusing, I have created an interactive flowchart to help you find a solution to the error. You should carefully read the question and select an answer by pressing one of the buttons
Could you ever log in to this account?
Can you log in to another account on the same device or same network?
Have you violated any Skype rules?
Do you have the latest version of Skype?
Most likely, the error occurs due to technical problems. Write in the comments more details about your problem, including the Skype version, operating system and a link to the result of the access verification test www.skaip.org
Download Skype on this page www.skype.com,
, then try to log in again.
Unfortunately, you cannot do anything but to wait until the developers fix the error.
Violation of the Skype rules leads to the account lockout, and in most cases it cannot be restored.
It seems you have forgotten your username or password.
Restore your account on this page a.login.skype.com
Have you confirmed your account using Microsoft Security Code?
Your account has not been registered. You should register again on this page go.skype.com