OK, I called Hulu Technical Support and walked through several steps with them, which I will relay. I'll bet Roku may feel a little differently about some of this, and it's a bit long (advance apologies), but here goes...
Bandwidth We first discussed bandwidth (I have 50/50, so should be not problem). 4K needs 16 Mbps per tech. They said lowest end of the Roku devices only supports 5-8 Mbps. I have an Express, which on the Roku site supports "HD" but not 4K or HDR, for which you need a Roku Premier. No worries, I have a 1080p HD screen, but not 4K. (Still get a great picture, so no complaints.)
Tested the connection and bandwidth under Roku, System, Network and all checked out fine, it saw 41 Mbps download. Didn't have an upload speed. If the Express can detec5 41 Mbps, don't know if the 5-8 mbps is all it can actually handle - or not. Cannot dispute one way or another - no documentation on that at the Roku site I could find. (Maybe a 'super user' knows...)
Fully Exit Applications Next, if applications on Roku are not exited properly, they can stay in device memory, slowing down the device - potentially contributing to instability. On my Roku remote, they suggested *always* exiting the application by pressing the 'back arrow' at the top (on my Roku remote, to the left of the Home (house shape) button) until prompted to exit the application. We have just been pushing the Home button to find/switch apps, not knowing that left the application in memory. [From my own tech experience, incorrectly exiting an application can contribute to instability.]
Delete and Reinstall Hulu As suggested by makaiguy above, we deleted the Hulu app and reinstalled it, just to ensure a 'clean' version of the Hulu application was installed. Yes, we recycled the Express between uninstalling and installing the new version of Hulu. (From Roku Home screen, highlight app, press * and select delete, OK. Recycle the Roku (Settings, System, System Restart...). )The tech handled the Roku login for me with the screen code provided, so I didn't have to do the painful login on the remote...) Next, just pressed the Hulu button on the Roku remote, and was prompted to add Hulu back - used the 'on screen' instructions to move it where I wanted it on the applications list (at the top left).
Device Age This is the part Roku may not agree with. When discussing the age of our Roku Express, about 2 1/2 years, they said they have seen some number of devices (particularly the low-end ones - which ours is) begin to fail in the 2+ years time frame. I'll see how mine behaves with the new information and steps above. 2+ years seems on the low end to me - I would think 3-5 ought to be more the rule, with most lasting even longer if not used 24x7. We watch <4 hrs a day - not heavy use.
So, too long a story a little shorter, the sound is working just fine, again. We will see if this continues for the near-term, since the sound going away happened 4 or 5 times in the last three days. *Assume* the sound is solved if I don't come back and post an update.
