Does anyone of you have an issue with the QHYCCD connection? I am having this issue on my QHY168C recently. I can confirm that it is not caused by cable because I manage to connect my QHY168C via NINA and SGpro from windows.
If you can open a terminal window on the Raspberry pi and enter tail -f /var/log/syslog and then connect your camera you can see if it successfully connects to the RPI4. I have had issues with a USB3.0 hub not having enough power to run the camera. A warning will show up in the terminal window if that's the case.
I don't think the RPI4 ports are powerful enough to run the QHY coldmos cameras.
Ended up I download Arm_32 and Linux_64 QHYCCD's latest SDK and manually installed them on my Kubuntu and SM OS/Astroberry. Now everything works flawlessly.