My philips sbc hc8445 wireless headphones have no sound, they were working last night, batteries are fully charged, everything connected properly & channels in sync, any advice would be greatly appreciated, Thank You in advance.

Maybe they just went bad. If you have replaced battieries, resynced, checked connections then I would suggest calling the manufacturer or at least the place you bought it.

The other thing to remember about these is philips bless there hearts have put a continuation loop into the battery dept this means if you don't use the philips batts chances are the batts you do use will have a outer seal all the way down the outside and you need to take of about 1/4 of inch from bottom so the batt connector at side of where you push them in recognise,s that they are there .when you look at batt compartment you will see a contact on both sides of the batt about 1/4 inch up the side foxed me whan I replaced my rechargables took all of two hours to work it out (cheep trick philips )hope this helps