There is a problem with the user's account, they can not login to the CP

[netregis]

Could you please help us to fix the problem with the Plesk, There is a problem with the user's account, they can not login to the CP. Everytime when the users try to log-in in the login page it's always shows "Login is incorrect". We really dont know what's happen to the account, the problem start after we change the user password. We absolutly sure that the password is correct.
So we have sent the issue in the Parallels' support website since yesterday, but there is nobody contact us back until now.. it's very urgently and strongly important.
Could you please help us....

Thank you somuch,
Sincerely yours,
Sabai Shop Co.,Ltd.