The issue due to missing of Primary key in the table. When EF mapping is done with a table which doesn't have Primary key, it is considered as a view & views being logical entity, cant be updated.
So either add the missing primary key in your tables or consider them as View & don't perform any update operation on them.
Go through below link how to implement Primary key in EF:
Manas MohapatraPosted Jul 21, 2016, 2:22 PM