Cannon Timer Buzzer

I have a Cannon cooker, model 10430G, 😀 , on which i have just replaced the timer control. All is working fine apart from the audible buzzer which should sound at the end of an auto-cook period or when the minute minder has been used,- it does not sound at all. 🙁 We had previously discovered by accident that if we press and hold a combination of buttons, pressing another will adjust the volume. (We didn’t make a note of this though!) 😥 . Nothing is mentioned in the user manual, and i can’t find anything on the web. I have spoken to cannon’s help desk and they advised that pressing the “minus” button when the buzzer sounds (or should be sounding) will adjust the volume but this is not making any difference. Can anyone please help with this problem? 😕