MobileMe sync not working for various reasons, fixes

The synchronization features for MobileMe and the calendar do not appear to function properly for some people. In many cases these problems stem from errors associated with Apple's servers, but for converted .Mac accounts there may be inconsistency problems reported by the service.

For server errors there is no effective fix on the user-end, and affected users must wait for Apple to iron out the bugs (see Apple's acknowledgement). However, users can attempt to reset their synchronization information to deal with consistency errors, and ensure synchronization is set up properly for automatic send and receive of updated information.

NOTE: Subscribed data (RSS feeds, calendars) will not be synced with the MobileMe service. For any subscriptions to be synchronized users must first convert them to local data.

Fixes

Reset the synchronization data On your Mac open the MobileMe iSync preferences (from the iSync menu or in the system preferences) and under the "Sync" tab select "Advanced". Then click the "Reset Sync Data" button and you will be presented with the option to replace all sync info or just one type of information (calendars, bookmarks, etc). Select the desired data type and click one of the arrows to ensure you reset in the proper direction. If the data on your Mac is current and up to date, then click the right arrow to replace the data on MobileMe. iSync will then re-sync itself, but it is also recommended to manually invoke sync again by clicking the "Sync Now" button.

Enable automatic synchronization This is required for the MobileMe "push" synchronization to work properly for some services. Many .Mac users have had their synchronization preferences set to either Manual or to sync at a specific interval, and changing it to automatic will allow the sync to occur when changes are made, resulting in the desired "push" behavior. Go to the iSync system preferences and in the "sync" tab ensure "Synchronize with MobileMe" is checked and set to "Automatically" in the drop-down menu.

Remove relevant preferences files After resetting the synchronization data and ensuring all contact and calendar data are available on the servers (albeit not syncing automatically), go to the ~/Library/Preferences folder and remove the synchronization preferences files. These are:

Workarounds

Manually synchronize If Automatic sync is not behaving properly after resetting all data on either the local machine or on MobileMe, use the iSync menu to manually synchronize the data. Go to the MobileMe "sync" system preferences and select "Manually" from the drop-down menu next to "Synchronize with MobileMe". Next, ensure "Show status in menubar" (at the bottom of the preferences window) is checked so the sync options will be available from the Mac OS X menubar, and use the menubar to manually sync all information.

Resources