ARC continues to be hit and miss. Also, if the audio is beyond PCM Stereo it may not work either. However try the usual. Remove all HDMI cables and then remove power. Wait 10 minutes and try only what you need to test this setup.
I won't ask about cable versions and such as most folk explode when asked.
If that fails, call it in and let Samsung repair the set.
Hi my samsung ue55hu6900 has no audio on 3 hdmi ports only picture,,ive tried several devices and cables plus my samsung soundbar wont do arc hdmi audio link up becsuse hdmi arc is one of the hdmi ports affected..tried resetting sound unplugging tv to no aveil??