I know there are a lot of variables here, but I thought I would give it a try to see if anyone has any ideas.
Have a Reolink E1 Zoom through the Reolink integration. Camera devices config is set to rtsp.
Set up Frigate addon through HACS. Created a Frigate card with my Reolink camera main stream as the camera stream. I also set up a Reolink card on the dashboard as it gives a lot of config options in addition to being able to watch the video. Both work fine, they stream live from the camera in both the main and sub stream (which I think Reolink calls EXT). Also works in the Frigate app, no errors in the logs, starts well.
But on the Andoid companion app, the video loads, but it doesn’t stream, the clock stays as it is. No movement, it’s like it’s a snapshot but the cards are set up for the video streams.
@woempiej pointed me your way, as I had a similar issue (which you can read about here if you want), which has been resolved.
I have a reolink video doorbell with 2 way audio working from within the companion app (android) using the frigate card and go2rtc. The Video auto loads and plays with audio, on load of the dashboard in the app - so I though I would share my lovelace frigate card yaml incase it helps you (below). Also - I had problems with using the http flv sources with go2rtc webrtc mode in the frigate cards directly, and had to configure go2rtc to use the reolink rtsp source to get it to work consistenty.