Check the player and source path
Use Roku’s comparison chart for the exact product, then install the genuine current Roku remote app. The mobile device and Roku must share the same wireless network. A phone using mobile data can have internet access without being on the network needed for this feature.
For Streambar and Roku soundbar products, Roku limits this feature to their built-in streaming player. Sound arriving from an external console or set-top box follows a different route. Identify the active television input and the app producing the programme before concluding that the headphones are faulty.
Connect the headphones to the mobile device
Plug wired headphones into the phone or tablet, or pair Bluetooth headphones with that mobile device. In the Roku app, select the correct Roku, open Remote and tap the headphone control. Begin at a low volume and adjust it after the route is active.
The television speakers are silent while Headphone Mode is active. Treat that as the expected output change rather than immediately raising the television volume. To return to normal room listening, turn the mode off in the app and verify the speaker level before resuming playback.
Confirm the normal viewing routine
Before relying on this for a long programme, practise connecting, changing the listening volume and returning sound to the room. Keep the phone charged and within a usable network connection. Compare the same passage with the normal speakers if a problem appears only through the headphone route.
A useful support report names the Roku model, mobile operating system, app version, headphone connection and active source. It should distinguish no sound, intermittent sound and a stable lip-sync offset. Those are different observations even when they occur during the same programme.