The optical character recognition works better with 720p video, and best with 1080p. (during testing the best results were with a phone running Camo configured to output 1080p) Position your camera directly above the play area with a perpendicular angle. The quality of recognition is also sensitive to lighting conditions: play in a well lit space and try to avoid glare.
Also make sure that you create and join a room with the right settings: the format and side are used to narrow the pool of cards that are searched, so must be selected correctly.
The video calls do not support audio. You have to use another channel like Discord for voice chat.
If you are playing corp, and your opponent is accessing cards from R&D, click this button and look at your screen, averting your gaze from your actual play area. You should see your own camera feed, blurred out and greyscale. You can then turn cards over for your opponent to access (what they will see see is still normal). Once you return them to your deck (or trash or steal them), tap spacebar to exit this mode and continue playing.