SIM settings for SQL Express vs SQL Server (full)

Known issue with SIM and SQL 2014. Unlike previous versions SQL Server 2012 by default uses virtual user account called NT SERVICE\MSSQLSERVER which is not supported by .NET and therefore by SIM.

https://github.com/Sitecore/Sitecore-Instance-Manager/wiki/KnownIssue-SqlServerDefaultAccount

Go to Services and change SQL Server (MSSQLSERVER) to NETWORK SERVICE (check names) on the LogOn tab. 

https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/scm-services-change-the-service-startup-account