Hi Paul,
Replace
"Data Source=91.186.30.8:8443\SQLEXPRESS;" with
"Data Source=91.186.30.8\SQLEXPRESS;"
The source should be
IP\SQLEXPRESS, also the user name for your database should be something difference than sa as 'SA' =
System Administrator 
Or the best solution would be a ticket placed to our support dept. They'll get it everything sorted out for you for sure...