You can reset a User's completion status from Completed or Incomplete to Not Attempted via the Users tab of an Activity.
Note: If you need to regularly reset the completion status of a particular Activity, you may want to consider using a Registration Rule.
Locate the Activity you need to reset the User's status for and go into its administration area (see find content in Find Learning or Content Manager if you're unsure how to do this).
You will see a list of registered Users. Search for the relevant User(s).
You can also filter the list of registered Users by completion status using the dropdown menu. You may only want to reset the status of Users who have Completed the Activity, for example.
Tick the box next to the User(s) name(s).
Note: If your intention is to manage ALL registered Users, make sure you click Select all items.
Choose Reset Status from the Actions dropdown menu.
A popup will open where you can confirm or cancel the action.
The selected User(s) completion status will now show as Not Attempted.