Unable to login to alternate/multiple accounts
This is a known bug/issue. Sorry you're dealing with it. Please try these steps since there seems to be a Cloudflare DNS issue affecting the login in some areas:
A VPN is working for many people. If you need a recommendation, Windscribe is free for several gigs of info per month. It is the one I use myself. Check it out in your app store.
See if you can get on the browser version on pc/mac, if that is an option: https://now.gg/apps/plarium/6886/raid-legends.html
Try clearing cache: From your Google Play Store, update WebView and other google related apps and see, if that will do the trick (it worked for some people already)
The error looks like this: