Almost always a signal-type limitation, not a fault. Zone 2 on most AVRs will only pass certain kinds of audio, and HDMI audio is the one it most often refuses.
The mechanics: the main zone gets the full decoding chain, so a Dolby or DTS bitstream arriving over HDMI is decoded and played. Zone 2 on many models is fed only from analogue inputs and from selected digital or network sources. Audio arriving over HDMI, and some digital formats, either cannot be routed there at all or can be routed only on higher models in the range. So your TV over ARC and your streaming box over HDMI play fine in the main room and the zone hears silence, because the AVR has nothing it is willing to send there.
Which sources qualify is a per-model fact, and I would call it the single most misunderstood line in AVR spec sheets. Check your model's manual under Zone 2 or multi-room; the table there is the answer, whatever the sales blurb implied.
Workarounds that actually work. First, use the source's analogue output where it has one, and connect that to the AVR alongside the HDMI; the zone can then take the analogue feed. Second, use the AVR's own network and streaming inputs for the zone; these are usually zone-capable and sound better than the analogue detour anyway. Third, feed the zone from a small dedicated streamer and amplifier of its own. That last option is often cleaner than fighting the AVR's routing table, and it lets the second room play something different without negotiating with the film in the first.
Planning multi-room from scratch? Tell us before you buy the AVR. A two-minute check of the zone table saves this entire problem, and it changes which model we would recommend more often than people expect. Send us the model you have and the sources you want in the zone and I will tell you which route applies.
Not sure what fits your room and budget? Share your room size and budget on WhatsApp. It is a two-minute answer with a floor plan.
