I too had trouble with the United Travel thing. I had to try 3 times to get it to work, but it eventually did for my CDG-EWR flight. At check in at CDG they did see my docs in the system so I didn't have to show anything other than my passport. No issues with the French app or getting a test.

UA is using the AC lounge all the way at the end of the terminal. It's quite a hike from security, but not too far to the UA gate. They have booze even at 7:30am, served by a bartender.