Chosen Solution
iPhone 3GS ringer mute button is flakey. Sometimes when shows it is off, it is realy on.
It’s a tiny plastic switch on the cable, it may have dislodged from the groove on outer switch. Try sticking oout outerwitch in mute position with some tape while re aligning plastic switch(in down position) into groove. It’s quite fiddly and takes patience.
dismantle it and find out if it is connected properly? iPhone 3GS Teardown look for the 6 and follow the cable upwards, unscrew that. then there is a screw on the side that holds it in place.
