I had the same problem of dead front panel audio port, i had a go at it several times, tried out a bunch of different stuff, nothing seemed to help, in the end what helped for me was going to asus page, find audio driver for my motherboard, which can be autodetected or manualy selected, download and install it. Attention it did not work even after rebooting my PC!! So lastly with little hope i went to control pannel under sound and devices as with so many previous drivers i installed and uninstalled, found the just installed driver, played a bit with its settings (turning on of different speakers to headphone settings) and suddenly works like charm.