I normally dedicate one usb port to the hard drive where I add photos and videos on almost a daily basis. The other usb drive is used for whatever I happen to need at the time: printing once or twice a week; flight simulator with my Taranis, and now my DJI RC. When this usb is not used by those, I have my bluetooth mouse adapter plugged in. I only have the two usb ports on my Macbook Pro. My hard drive has two more usb ports which I use for charging usb devices.
I have tried plugging the dji air unit into both usb ports. The few times that the air unit did connect, with both my TinyHawk2 and the GEPRC Rocket Plus, the usb connection appeared in the dropdown list almost immediately. When I first activated the air unit on DJI Assistant 2, I did not update the firmware, and this is also true for the goggles. I noticed that I was not running the latest firmware when I was, and still have binding issues between goggles and air unit, so I updated the firmware on all three FPV components. I doubt if that has anything to do with Betaflight connectivity, but I just thought I would mention it. Finally, yes I will try again waiting before I click connect, but I am fairly certain I have done that before.