Seems odd. Sonos has no idea what is sending the signal, other than the TV is at the other end. I’d be tempted to check the TV set for any updates, apply them, and reboot the TV by unplugging it from the wall for a couple of minutes. That might force a reboot of the Hulu app, and get you sound. 

Beam Gen 1 at a guess, Hulu sending DTS at a guess (or Dolby 1.0), which are not supported.

Can only guess given the lack of information provided.

Ah, good point, I had assumed that CEC was working properly and was sending back ‘acceptable format’ data to the CEC processor running on the TV set. The power cycle I suggested should fix that, though, I’d think. 

The Beam (Gen 1) does do DTS, but no DD+, I think. I know of no mainstream streaming service that sends DTS (though Hulu isn’t available in my country).

But the CEC connection in the TV should be polling the HDMI connected sinks for appropriate codecs….unless the CEC has been turned off.

Only on S2 though, no DTS on S1. Or older Samsung TVs.

Until the OP provides additional information, I think we have speculated as much as we can.