Messages Backup and Sync

I have followed all the guidelines for setting up backup and sync. I have entered pin after pin after pin on each device I try. I either get a landing page that says “hey, you’ve got a lot of messages. Please wait while we load them all” (but it never does, and the webpage is all jumbled), or a “hmmm something went wrong” 

i have cleared cache. I have turned iMessage off and on. I have cleared history. 

The webpage isn’t working. It’s not a troubleshoot issue on our end, this is an att website issue.