Most likely you are inserting if you are not receiving an error. I cannot see your code but I would hope you have done a try/catch to make sure there are no errors.
If there are no errors then the next step is to make sure you really need a user instance. A user instance will not update the master database. It is actually copied to a "local" instance of the database.
To check to see if it is inserting properly you can use a datareader to connect to the database, do the insert and bring back the results. This should confirm the insert statement has done what it is supposed to.
Again, the insert statement in a User Instance will only apply to the user instance NOT the main database.
For more information:
Connecting to User Instances[
^]