I have a Sony bluray surround sound and lg smart tv, I can't play my Apple TV sound through my hts, all my connections are hdmi and both systems have arc, please help?

Is your Apple TV connected to the Sony or directly to your TV? If directly connected to the Sony HTS ARC shouldn't be needed and you should have audio. If that's the case check the Apple TV settings to be sure it isn't set for s/pdif output. If connected to the TV then the TV should be able to put a s/pdif signal on the HDMI ARC pin but perhaps there's no way to assign it to the HDMI input coming from the HTS? It may be going to the ARC pin on the Apple TV HDMI input which won't give you any sound. Normally ARC is intended to put the s/pdif signal from the TV's internal tuner on the HDMI cable from the HTS so the HTS can play TV sound without having to tun a separate Toslink cable from the TV s/pdif output to the HTS. One other thing: Early HDMI cables do not include the ARC wire so be sure you have ARC capable cables. Look in your TV documentation to see if there is a way to assign the ARC output to a different incoming HDMI input if the Apple TV is connected directly to the TV. If not you may need to resort to a Toslink optical cable from your TV to an optical input on your HTS. Or actually running that cable from Apple TV to the HTS would be better since it's possible it could carry surround sound. Most TV's optical outputs are limited to the 2 channel sound the TV can accept.