This error occurs when Ultimate To-Do List is synchronizing with a Google account on your device, but there is an issue with that account in your system settings. For example, the account may have been deleted.
Follow these steps to resolve the issue:
Visit the accounts area of your device's system settings and make sure the Google account you are syncing with is listed there, and there are no login or sync issues reported. Add the account or resolve the sync issue.
- Visit the Apps area of your device's settings and open the settings for Ultimate To-Do List. Tap on the Force Stop button to ensure Ultimate To-Do List is fully reset when you open it.
- Open Ultimate To-Do List and run a manual sync.
If these steps do not resolve the issue, then try the following:
- On a desktop or laptop computer, visit google.com/calendar or gmail.com and log into your Google account. Click on the tasks button on the right side of the screen to open your task list.
- Open Ultimate To-Do List and compare the tasks on your device with the tasks you are seeing in your browser. If there are any tasks on your device that are not appearing in your browser, type them into your browser. This step is necessary to ensure no tasks are lost.
- Uninstall and reinstall Ultimate To-Do List. On the opening screen, choose the option to link to a Google account. Do not choose the option to restore from backup.
- Select the Google account and your tasks will download to your device.