MSSQL sa user keeps getting locked: Login failed for user ‘sa’

Symptoms

• Database server keeps getting disconnected (the icon is greyed out in Tools & Settings > Database Servers);

• The following error is shown in the %plesk_dir%adminlogsphp_error.log:

[2018-05-08 15:22:36] ERR [1] "C:Program Files (x86)Pleskadminbinmssqlmng" --check "--server=.MSSQLSERVER2016" "--login=sa" "--password=*****" failed with code 1.
stdout:
Login failed for user 'sa'.
at (VADOConnection::open line 48)
at Unable to ADO conect with connection string: Provider=SQLNCLI11;Initial Catalog=master;Data Source=.MSSQLSERVER2016(VADODatabaseProvider::connect line 182)
at execute console command --check(vconsoleapp::start line 93)
at execute "C:Program Files (x86)Pleskadminbinmssqlmng" --check "--server=.MSSQLSERVER2016" "--login=sa" "--password="(vconsoleapp::run line 110)

• The sa user is locked out as it can be found in SQL Server Management Studio > Security > Logins > sa > Properties > Status:
  
  

• The sa user keeps getting locked after the unlocking.

Cause

Password Policy is set to lockout the account after a certain number of failed login attempts.

Resolution

1. Connect to the server via RDP;

2. Go to SQL Server Management Studio > Security > Logins > sa > Properties > General and untick the Enforce password policy box: