When you are trying to upgrade to a newer ITMS (IT Management Suite) version, you can't because SIM says the following:
"You have selected an unsupported SQL instance of Microsoft SQL Server for currently selected Platform. Select a different server in order to continue"
ITMS 8.x with a newer SQL Server version
Working as designed to avoid installing on unsupported SQL Server versions.
In order to pass this message, you need to be in a supported version of the SQL Server for the ITMS version that you are trying to upgrade to. Refer to Microsoft SQL Server Support Matrix
In most cases, you can upgrade your SQL Server or move a copy of your database to a newer version of SQL Server (refer Moving an Existing CMDB from One SQL Server to a New SQL Server) and then try to upgrade your ITMS version.