Hello,
When I open Anki (on Mac), a message “Synchronizing with AnkiHub” appears and shows a loading screen. I have no way of stopping the loading screen except by force close of Anki. I am not able to access my decks.
Hold shift when starting Anki, delete the AnkiHub add-on, reinstall it, restart Anki, and resubscribe to your subscribed decks.
That should solve your issue 
Worked perfectly, thank you for your help!