What phone system are you using.. android or iOS? What model phone? I feel the mcoc update keeps requiring faster processing and memory.. I myself am using a Samsung Galaxy S10 plus with 512gb microSD (forgot which brand but it was the fastest microSD available when I got it). Occasionally I'd get disconnected from the game.. so my guess is the server is not able to handle the volume of users or its not optimized to handle the high influx of users.
I just logged on right now and everything works for me. Check your internet connection and/or try restarting your device. Sometimes that can help.