I've been using my iPhone for DoIt.im for the past 6 months. Now, when I try to sync with the Web, the web doesn't know of any of my completed tasks. When I check my iPhone sync log, it says that it synced successfully. When I click the spiny button on my iPhone and on the web interface, nothing happens. I have not yet attempted to install the desktop app for Windows.

I have a Pro account, which I purchased yesterday.

Other symptoms of this include an error (412) when trying to sync with Google Calendar.

Please advise what next steps I should attempt.