In my case, streaming worked with QGC (you have to wait a bit for the stream to start / maybe restart your camera while QGC is running) but not with Solex (Error: “Video not supported”).
Connecting a running flight controller to the air receiver (UART air unit <-> Telem1 Cube Orange) “solved” the problem for me -> No Error in Solex anymore.
Anyway, 5V seems to be to minimum voltage, use something between 7-10 V.
I’ve increased the power to 7V and reconnected/restartet the camera and system several times but wasn’t able to get a Video stream. Do you have any other idea? Picture of my setup attached.