Marvel Contest of Champions Stuck on “Signing In” Screen and Won’t Open

In the game Marvel Contest of Champions, I’m experiencing a serious login issue — the game won’t open properly. After making a purchase, I can no longer log in. It says “Signing in,” but then freezes on that screen. Only the background music plays, but the game itself never loads.

I tried deleting and reinstalling the game, but it didn’t help. I even switched to a different device, yet the same problem persists. Can someone please help me? The game’s name is Marvel Contest of Champions.