Mobile service class is not used in this situation.
It seems like MySQL is preventing records from being inserted. Any warnings/errors in the MySQL logs?
If you turn on debug and debug_log in wp-config.php (define true) you should see any issues, including MySQL issues in the ./wp-content/debug.log file.
Just make sure you do not leave that on very long on a live server and be certain to not only set those back to false but remove the debug.log file when done.