Cannot log into the Plesk interface with username and password for Subscription: You have entered incorrect username or password

Symptoms

• Not able to log into Plesk GUI by using the valid login credentials of the system user of a Subscription, while seeing the following error in a browser:

  PLESK_ERROR: You have entered incorrect username or password

  

Cause

The system user of a Plesk Subscription does not have access to the Plesk GUI by design.

More details on what the system user in Plesk can do are available in the following article:

What is the meaning of a "system user" term in Plesk?

Resolution

Since system users do not have access to Plesk GUI by design, if you want to allow someone access to the Plesk interface, you have to create a new Additional User for the Subscription.

Alternatively, you can create a separate Customer and change the Subscription owner to become that new Customer, because Customer accounts in Plesk do have access to the Plesk GUI.