Really, the first thing that you should check is that the App_Data/n2_host.config file is set up correctly.

1.) There were a few online recommendations to try various edits to IIS (e.g, enabling 32-bit apps, turning off .NET 4.0 and then renabling, etc.) I ran through a number of these.

2.) Server/File Permissions --- the IIS_Usr needs to have permissions in the files and a standard 'migration' did not inherit these permissions, of course. This is pretty amateur here, but permissions are (clearly) important.

3.) There was a database error in SQL Server that had a username incorrect. (TIP: IIS errors are often incomplete: look in the server event log for additional, more helpful, details) I'm sure this was crucial.

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