I had the same problem and I figured out I could not submit a new build because the previous one was still submitted for review. So you need to ensure that your previous build is not submitted for a review yet. Then you can remove the build and upload a new one.

I had the same problem, the developer mode was not available in security & privacy. Here is how I resolve it : Unplugged my iPhone. Restarted my iPhone. Plugged it back in. Opened > closed > re-opened Settings I did not restart Xcode nor my Mac, left them opened during the whole process. And the developer mode appeared. Weird...