This has happened to me a few times now and every single time I had to spend quite a bit of time sifting through the blogs looking for answers. So I finally decided to document it for myself here.
These are the steps:
- Go ahead and restore the MDS database on the server of your choice (running SQL Server database engine, obviously)
-
Go to MDS Configuration manager, check if all the MDS settings are ok. It should give you fat check marks like this
- Click on Database configuration and connect to your MDS database… you may need to Upgrade your database if necessary
- Go to the Web configuration next and create the new web app if necessary
- At this point, if the user account who was the administrator is no longer accurate in the new environment, you will get “Access Denied” error when you try to go to the MDS Web Application, so don’t do it
- Connect to your MDS database from SMS, find the mdm. tblUser table, right click and Edit it.
-
You will find a row that looks like this
- The reason you are getting Access Denied is because the SID and UserName values are no longer applicable, so you need to enter the SID and UserName for the new user who will be the administrator of the MDS
- Go to Command Prompt (as admin if necessary) and type wmic useraccount get name,sid
- This command will return a list of user accounts and SIDs, enter UserName as YourDomain\useraccount, and SID just as it shows up in the list from the wmic command and commit your changes to the table, restart your IIS and you should be all good to go…
business intelligist 
Nice find.