I am having the same problem. I have a Roku StreamingStick 4K+ which I just purchased last month. The remote is paired with my Insignia TV and all functions work perfectly except for the headphone jack. I plugged in a pair of known good headphones into the remote. Immediately the sounds cuts off on the TV and the headphone icon appears on the TV. When I adjust the volume on the remote, it shows the number increasing on the TV screen but I hear no sound. If I unplug the wire from the remote, the sound comes back on.
I have tried all the debug tools listed, including power off, power on, re-pair, etc. The headphones are known good and work fine on my laptop. The wire connects perfectly into the remote and, as I said the sound cuts out on the TV and the headphone icon appears on the TV. The remote is fully charged.
I am not interested in using the Mobile App for private listening and just want to get this remote working properly.
What do I do? Thanks!