I’ve run into this problem a few times now, and in (almost) every single case I’ve found that persistence is usually all it takes to solve. By that I mean that while the first launch may hang, a subsequent launch may complete the preliminary sync and send you on your way. Or maybe a reboot, then a subsequent launch.
I know that’s not much of an answer, but I run Shaxpir on several PCs at home and I’ve seen this (or similar) syncing issues that were solved using this method.
Another step to keep in your back pocket is the wrench icon in the corner of the logon screen. Clicking it will take you to a window with a button that allows you to clear your local cache. Be warned that this action will remove any non-synced local data, so use with care. Still, this has helped me out before.
If I’m still having trouble at this point then it’s time to reach out to Benji via the support page (http://support.shaxpir.com/). He’s always been fantastic about getting me back up and running if I run into problems.