To remove a Skype for Business Server backend SQL database, you execute the following and immediately hit a similar failure as depicted:
Uninstall-CsDatabase -SqlServerFqdn fesqlserver -DatabaseType Monitoring
Trying to connect to Sql Server using windows authentication…
Exception stack:
Type: System.Reflection.TargetInvocationException, Message: Exception has been thrown by the target of an invocation.
Type: Microsoft.Rtc.Common.Data.DbSetupSqlServiceNotInstalledException, Message: Failed to find Sql Service. Make sure that SQL server service (default instance) is installed in machine fesqlserver.Uninstall-CsDatabse: Failed to connect to the SQL Server fesqlserver.
At line:1 char:1
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For a setup with non SQL default instance (MSSQLSERVER), specify the -SqlInstanceName parameter and corresponding value to correct this issue.