We have ArcGIS Online configured for "enterprise" logins to authenticate against our MS Active Directory. I can add users from AD by sending them invitations in ArcGIS Online. They must respond to these emailed invitations for their account to be created in ArcGIS Online.
I would like to add AD users using the option, "Add members using their enterprise ID without sending invitations". This gets their account set up immediately, and then I can add them to groups, etc, without waiting for them to respond to an invitation.
However, to use this option, I have to include the user's "Enterprise ID".
What is this Enterprise ID, and how do I find out what a particular user's Enterprise ID is? Is it something I have to get from Active Directory? If so, how do I find it for various users?
(I have tried various combinations of username, email address, and organisation name and underscores, but with no luck.)
UPDATE
As per comments, I have now tried populating the "Enterprise ID" field using the format, DOMAIN\user.name (and DOMAIN/user.name), but it will not accept anything with either a \ or a / in it (no error, but the "Next" button does nothing). As soon as I remove the (back)slash, the "Next" button works as expected (but the account does not work because I don't know what I'm supposed to put in the "Enterprise ID" field.
I note that the examples in ESRI's documentation do not use this format. The examples there are "jonc1111" and "sati3554". See: https://doc.arcgis.com/en/arcgis-online/administer/invite-users.htm#ESRI_SECTION1_D4222EB63EF14C96BF37F1A098F37AFA
I feel like there's something very simple/obvious that I'm missing, like I'm looking at the problem through the wrong lens or something. I just can't figure out what I'm sure is supposed to be straightforward.