I have an HDHomeRun Prime & Extend online, using a Fire TV 4K (Ver 3) with Channels DVR 2.0.7
Turn on TV first thing in the AM, go to Guide – all is good.
Turn off TV
Come back a few hours later, Turn on TV, three channels in Guide (Weather from Extend and Travel & Weather from Prime).
Unplug Fire TV then plug back it has to find the DVR again, but when it does, I have a Guide.
The guide is available 100% of the time on DVR Remote and in Plex.