After OneNote Mobile for iPhone hits the news wires, the response, demand and downloads of the app has been tremendous, which rightly fulfills the aim of Microsoft to promote OneNote, one of the best note taking application in the market.

iPhone-based OneNote Mobile app has been getting various errors such as “Login failed, error: 400” message when trying to sign in to Windows Live ID on initial app load, which Office team blames on overwhelming interest in the app and cause intermittent cannot login to OneNote mobile issue. The login issue has since been resolved, but apparently some users face another problem.

After logging into OneNote Mobile on iPhone, iPod touch or iPad, some users have encountered the following error message:

Loading list of notebooks failed. (500)

The error normally happens only on users with a brand new Windows Live ID account. The same error also happens when users attempt to sync the notes on mobile phone with the cloud in Settings -> Sync Now.

Apparently, in order to sync with the OneNote Web App on Windows Live, user also has to sign into the web. Thus, to resolve the issue, try to sign into Office Web Apps using the Windows Live ID at at least once to accept the terms.

Once signed in on web, try to sync the OneNote Mobile for iPhone again, and it should work properly.