When I previously encountered problems like these, I discovered that removing the table from the model was the best solution. Save the model, then exit. Reopen the model thereafter, and add the table again.
However, if you don't want to delete the table (for instance, because of a connection to another table), you may use the following alternative solution: Ctrl + F to locate a line similar to this one in your edmx file after opening it in an xml editor.
Property Name="Email" Type="Binary" Nullable="false" MaxLength="50" FixedLength="false"
Change it to:
Property Name="Email" Type="String" Nullable="false" MaxLength="50" Unicode="false" FixedLength="false"
Keep it and rebuild it.