I ran into another issue after upgrading a FIM 2010 deployment to MIM2016. As part of the OS/Infrastructure refresh I moved the database to a more recent SQL server platform. One of the things I initially forgot but found out pretty quickly is that obviously I also needed to update the FIM Management Agent parameters so that it points to the new database location. However when I clicked OK, I got the following error:

In words: Failed to connect to specified database. Failed to connect to the specified database with the given credentials.

And in the Forefront Identity Manager Management Agent event log (on the FIM Sync server):

In words: mmsmafim: MIIS.ManagementAgent.ManagedMACredentialFailureException: Failed to connect to the specified database with the given credentials.
   at MIIS.ManagementAgent.RavenMA.UIValidateCredentials(String pszCredentials, Int32& pfValid, String& ppszResult)

Upon looking a bit deeper I found the following error in the SQL Server logs:

In words: Login failed for user 'CONTOSO\FIMSYNC'. Reason: Failed to open the explicitly specified database 'fimservice'. [CLIENT: 10.x.y.z]
Error: 18456, Severity: 14, State: 38.
This was a bit odd, it was complaining that the FIM Synchronization Service account had no access to the FIMService database. I’d expect the FIM MA Account to be used for this connection…

I checked the old database/SQL and I could confirm the FIM Sync service has no access to that database… As I didn’t wanted to start handing out permissions on a wild guess I started googling a bit. I came up with this TechNet thread: TechNet Forum: FIM 2010 Update Rollup 2 Problem which suggests granting the FIM Sync service account the FIM_SynchronizationService role within the FIMService catabase:

Of the FIM MA configuration again. Attempt #2:

In words: Unable to update the management agent. The object explorer specified was not found. (Exception from HRESULT: 0x80070776)

Back to google gave me this thread: Technet Forum: Strange stopped-extension-dll-file-not-found error where Craig suggest rebooting the FIM server. I rebooted the server, undid the SQL changes. And tada! It seems all the Synchronization Service needed was a good old restarted. Perhaps restarting the sync service was good enough but I rebooted it anyhow.

Conclusion

I was having troubles reconfiguring the FIM MA and I was able to resolve it by just rebooting the sync server. Configuration changes on SQL were not required.