I never see the contacts I added via the users interface on the "add members" list of the group interface. I do see some other external contacts however, which makes it more mysterious. I see no difference between the ones I do see and the ones I don't see. The contacts were added weeks ago so it's not a propagation issue. The "bad" contacts do appear in the Outlook client Global Address Book.
These contacts are all similar in that they have only a name and an email address. The email address' are all for their individual Mobil numbers in order to email text messages to them in the event of a downtime issue. Eg:Email address removed or whatever their provider uses. I did create a distribution list for just this bunch of contacts. But now I want to also add them to another 365 group and they aren't there.
What would make them not show up but other contacts I created do show up? I am the admin, and again, I have checked all the points in the document linked at the top of this posting.