Have you encountered a situation where Connection to Plesk Control panel fails with the following error: Detailed description or error message text : ERROR: PleskMainDBException <b>Source:</b> Microsoft OLE DB Provider for SQL Server<br/>
<b>Description:</b> [DBNETLIB][ConnectionOpen (Invalid Instance()).]Invalid connection. 0: common_func.php3:601
db_mssql_connection() 1:
common_func.php3:630
reconnect() 2:
common_func.php3:591
db_connect() 3: auth.php3:90
This will occur when Plesk is used with MSSQL Database and MSSQL instance (hostname,port) is not set correctly in the registry.
Solution to this problem is to make correct to the registry value. Check for the MySQL_DB_HOST in the registry HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\PLESK\PSA Config\Config
Make sure that MySQL_DB_HOST sets correctly to valid existing MSSQL instance (example, .\SQLEXPRESS). If the instance name is wrong please correct the name and restart the Plesk panel and MSSQL srever.