If you are using a Mac, there's a possibility where you may run into a situation where the tags you add to a user don't save. No matter how many times you switch the tag to "on", it just won't save.
To fix this, all you need to do is go to the user's profile whose tags won't save. Find the tag that you're trying to save, flip it on, then enter a start and end date in the date boxes over to the right. This will help keep the tags saved!