During SCOM 2016 install the DB installation fails – When I look in the install log it says the login failed, but it’s got sysadmin?

HanSolo selected answer
    • https://blogs.technet.microsoft.com/kevinholman/2016/10/22/opsmgr-2016-quickstart-deployment-guide/ If you haven't already then it's worth following along with Kevin Holman's guide. Are you all 2016 i.e. SQL 2016, Windows 2016? 
    • What does the SQL log say? Can you get some extra info regarding the login failed?
    • It's not something unrelated to permissions, such as firewall blocking between management servers and DB server?
    • I found this in the setup log: Error: :Exception running sql string [NOT DEFINED]: Threw Exception.Type: System.Data.SqlClient.SqlException, Exception Error Code: 0x80131904, Exception.Message: Cannot open database “OperationsManager” requested by the login. The login failed. Login failed for user ‘Domain\User’. SQL logs just echo this..