I have a Panasonic KX-TG5453 phone system (3 handsets with answering system on base) that was bought at Costco. Just recently the base unit has no volume. When someone leaves a message I cannot hear it or when I press the play button there is no sound. I adjusted the volume up to 8 and still nothing. The only way to listen to the message is through the handsets. Any help would be great. Thanks!