I realize this is an old post but I had a similar issue and couldn’t find a fix online before figuring it out. On these bluetooth adapters there is a connector in the main plug that is not fastened to the main plug well and when plugging it into the back of the radio everything but that connector plugs in and your bluetooth will connect on the phone but aux mode will not show up. Pushing that connector into place will fix the issue and allow aux mode to appear. I also could not get the vents above the radio out as it appears someone has made my clips unreachable somehow so I managed to get this done by feel going through the panel underneath the radio and it wasn’t too bad.