After dealing with screen flicker on the S4 and 3.9 for a while now I decided to go back to 3.8 since it is impossible to work with 3.9 unless you are a stroboscope :)
I launched 3.8 from my backup folder and it just starts and closes after a split second. Which is an old issue with Pro 3, sometimes this works and sometimes it doesn't. No such issue on mac machines which I prefer for Djing but I have to use this PC because I'm currently running Traktor on my backup machine with some old AMD GPU.
When I started 3.9 it immediately asked me to login into Beatport Link and I was able to log successfully. I don't know if it is linked to the issue with the backup version (3.8.0.46) not starting but it seems to be related and could hopefully help identify the problem.
Best,