The strange thing is, it was working fine a few days ago. I added a new column to a table and was going to update the model through the designer and now it says "The Entity Data Model Designer is unable to display the file you requested. You can edit the model using the XML Editor."
There's nothing particularly noteworthy about the new field, it's just a non nullable bit field in SQL Server 2008.
FOR Visual Studio 2017
I searched for the solution but come up with the installation of some NUGET packages and Extensions, nothing worked out.
Solution (Missing Entity Framework on Visual Studio)