I sent an email to support@insynchq.com but wanted to follow up here as well.
I have experienced this issue before, and I solved it by resetting and starting the sync over. After syncing over 100gb (LOTS of small files), InSync is not stuck at Signing In… It never appears to actually sign in. I really can not afford to start the sync process over again.
Not sure what my course of action should be.
