If you're still having trouble getting that single sensor to initialize, double-check that your voxl-camera-server.conf file is strictly set to only enable that specific physical port. Sometimes the server tries to look for the default stereo pair and throws an error if it doesn't find both.
It also helps to run voxl-inspect-cam -a just to see if the hardware is even being detected at the system level before diving deeper into the JSON settings.

I have the same problem before — turns out the compass setup finally worked after I did a full sensor recalibration in QGroundControl and made sure the GPS/compass was facing the right direction. Worth a try if you haven’t done that yet!
You can also try this tool for free. https://123compass.org/