Haven't been able to log into Duel Links with mobile data for more than half a year now. It only shows the Konami-Anniversary screen and then a black screen with the yellow loading-animation. I have waited hours on this screen but it won't ever connect.
Could be your phone settings. Check if Duel Links is allowed to use your mobile data.
Due the provider maybe, I change to another mobile data provider or connect a hotspot with different provider that has been blocked and it worked.
I have the same problem, i did reinstall it nothing change
My suggestion is "Use VPN" To login/open and deactivate it
It's either Konami or your provider that make this happen (since 5.2 i believe)
you downloaded a hacked version of the game, play legit...