SQL Server connection string invalid

Good day,

During installation, my named SQL server instance path: SQLSERVER\INSTANCE was accepted BUT upon checking the database, the schema was instead installed to the default instance SQLSERVER\MSSQL.

I went to check in “Connect Server Configuration\Database Connection” and see my settings are configured correctly BUT I cannot leave the page due to “invalid hostname” error.
I can change just to hostname ot IP of SQL server BUT as soon as I add the “” to input the instance name it reverts to “invalid hostname” error.

Please help!
Thanks

To specify the instance name, add the instanceName property separately as seen in the below screenshot