Tethering Express 4k+ to iPhone, says it's connected, almost nothing streaming
New Roku user. Bought and successfully activated an Express 4k+, connecting to internet by tethering to an iPhone 7. I checked the connection in "Settings" device reports connection is "Good" or "Excellent." I can see channel icons on Home screen. Selected Roku channel, it comes up, but no specific content is shown--just empty rectangles where content choices would be displayed. Went to youtube--specific content is displayed, but if I click to anything specific, progress indicator spins for a while, then blank screen. I searched youtube for some specific content and clicked on some of the results, a few, maybe 2%, actually play, otherwise spinning dots for a while, then blank screen.
I have successfully streamed video before with same tv and phone, but with a firestick.