Whenever I hit sync, I get the popup box saying “downloading deck…” but then it never completes (the bar is already at the end; the box just never goes away). I then can physically close the dialogue box, and then the deck finally syncs. I have no idea why this is happening, and it’s annoying. The popup will not go away without manual input.
This issue does not happen when I am signed out from AnkiHub.
Hello,
There seems to be a glitch related to syncing that just popped up in the last few minutes. I’ve made the developer team aware of it so hopefully we’ll find a solution in short order. Sorry for the issue (it’s happening to me too) and thank you for your patience. 
In the meantime you can disable your Ankihub addon and Anki should run smoothly otherwise. I’ll have an update for you as soon as is possible.
Awesome, thank you. You guys are the best.