Update query is not working
As a matter of debugging, if you have the Devel module installed, try executing the query at devel/php with hard-coded data. That will help understanding if there is an issue with the  db_update(). Also, when you run the query and an error occurs, the error log at admin/reports/dblog on your site should show you any error message about that query.

In case you need to update or insert values on a table, db_merge() should be used instead of db_update(). db_update() doesn't insert new rows, but updates the existing ones; db_merge() updates the existing ones, or creates new rows. 

Once you are ready with a working query, debug the $form_state values; there might a mismatch between database table column type and the data you are trying to put there.