DBA cockpit connection XXX cannot be established

Symptom

The following error happens on step 5 'Enter System Parameters' when setting up the 'Managed System Configuration' via Solution Manager Wizard.

         DBA cockpit connection XXX cannot be establishedDetails errors would be
         SQL error 10054: TCP Provider: An existing connection was forcibly closed by the remote host. 
         or
         SQL error 15151: Cannot find the user "XXX_SAPMonitor"  
             
    If the DBA Cockpit Connection Status is greyed out, it means no DBCON entry was found. The connection can be set up from the beginning.
        If the DBA Cockpit Connection Status is in green light, it means an existing DBCON entry was found. The Authentication type and monitor login name cannot be changed.
2, Administrator login.