Are you attempting to edit a SQL 2014 database with the 2012 version (or earlier) of SQL Management Studio?
You can determine the SQL version of your database by running this query against your master database:
SELECT @@VERSION
I had the same problem and I was able to direct edit tables (‘Edit Top 200’) by installing and using SQL Server Management Studio 2014. Even if both your DB and Management Studio are version 2012, it might not hurt to upgrade Management Studio.