You may not need to send it in... if you're using rechargeable cells in the transmitter and you charge through the charging jack in the transmitter handle, that might be your problem... the M11 has a switch in the charging jack that prevents the radio from being turned on when the charger is plugged in. Sometimes this switch gets stuck and prevents the radio from turning on even after the plug is removed.

Try plugging the charger in and unplugging it a few times. This sometimes solves the problem completely.