Adding free-plan users to organization


I am confused about adding free users to the organization.

I have a number of full licences, with a number of free accounts collaborating as guests. Some of them have been able to sign up for the free account and they appear in the organization; however, others do not appear in the organization. What could be the reason for this difference? The region is the correct one.

Additionally, I don't see a way to manage free accounts - I need to navigate to a group to actually see them, as they do not appear in the users list. Am I missing something?