“Cannot insert the value NULL” into column X, means column must contain a value (cannot be empty).
Assuming Id column is your primary key, you must provide a SQL Statement to generate new value for insert.
Please check you Primary key setting Assign Table -> Mandatory Keys.
Possible statements per datatype:
Guid:
int auto identity(also Auto Increment, AutoNumber etc.):
select @@IDENTITY , Identity column must be set to Yes!
int (NO Auto Increment):
select ISNULL(max(YOUR_COLUMN_NAME)+1,1) from YOUR_TABLE_NAME