Using latest Entity Framework 6.1.3 with Visual Studio 2015 and connecting to SQL Server 2016 developer edition, I had the following error:-
Could not determine storage version; a valid storage connection or a version hint is required.

Fix:-
In Visual Studio Solution Explorer.
Right Click over the Entity Framework .edmx
Open with and select XML Text Editor
Search for "ProviderManifestToken=" and either you will have XXXX or in my case I had 2012 in this value. So I changed it to 2008 and now my code works.
Migrating some Excel Automated code using C# off an old Windows 2003 Server onto Windows Server 2012 R2 and using Scheduled Tasks to run I notice it was failing. User linked to the Scheduled Task has correct permissions and it is being run with highest privileges. Excel installed and I can run the code manually fine as that user. Plenty of threads about the issue but the only thing that worked was:-
FIX
Windows 2008 +
Add 2 directories:-
%windir%\System32\config\systemprofile\Desktop
and
%windir%\sysWOW64\config\systemprofile\Desktop
Windows 2012 r2
Add 2 extra directories:-
%windir%\SysWOW64\config\systemprofile\Documents
and
%windir%\SysWOW64\config\systemprofile\AppData\Local\Microsoft\Windows\INetCache