Willing to make a bet this is a server issue as everyone is reporting the same symptoms across all platforms. Think about what happens when upgrading an artifact your device will establish a connection with the server to update your artifact status that is then available on all devices. I am going to try and install VPN to see if that resolve the connection issue. 

The exact same problem is happening again with the latest release 4.60.2 across all platforms.  I have followed all the instructions for reinstalling, rebooting, etc. This is a developer/QA issue that is only experienced while playing this game. I am on day 84 where I have played for hours per days and have seen zero problems with the champ list until the 4.60 release.  

Removed personal info.-Q

Upgrading artifact didn't resolve for me, neither did sacrificing a champion (I've had the issue for over a week, and done multiple of each of these "solutions".) The issue is occurring not only on PC (Plarium Play launcher) but on my Samsung Galaxy phone as well.