I got this error. I logged in changed a deck earlier and then closed the game. Been stuck on unable to authenticate and then lost connection. its a rinse repeat. Type in my password when given the chance to login and repeats the cycle. I've checked version, server status, and my internet. I have tried mobile and pc and both are doing the same thing.
31/08 same issue with server up
same problem - the issues since the last update make it hard to get my Mastery point for each day
It is the second time I have this problem ... the first time it was fixed with the new game update ... but I could not play for 5 days ... UNACCEPTABLE !!!
[Deleted User] commented
The server is down while the major update is being installed. Always a good idea to check the status page: https://magicthegatheringarena.statuspage.io/