Entity framework can read but not write

See more:

connection

Hello

I am using a simple data-first EF model to update a db in my remote Sql Server instance.
In My application, I first call a stored procedure from the model , which simply reads the date of the last update on this db, and it seems to work fine .
But when I use the entities and then try to update the db, I get the following error :

"remote server connection failed"

which is kind of strange since just before I used the stored procedure to check the date.
I am using the "sa" user , with the right password , and I should be able to read/write from/to the db.

The connection string I am using is :

...add name="MyDbEntities" connectionString="metadata=res://*/DataFirstModel.csdl|res://*/DataFirstModel.ssdl|res://*/DataFirstModel.msl;provider=System.Data.SqlClient;provider connection string="data source=LENOVO-PC\MSSQLSERVER2014;initial catalog=MyDb;user id=sa;password=password;MultipleActiveResultSets=True;App=EntityFramework"" providerName="System.Data.EntityClient" />

what is happening ?