Sounds very similar to a bug I just posted up a few days ago and awaiting comments. https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2018/11/content-approvals-with-azure-ad/
Are any of your users in your database tables?
So as far as I can see the ISynchronizingUserService syncs the users in to the [tblSynchedUser] table as users login to the system, as you said they seem to be there and in that dialogue for access rights but they aren't appearing in some of the newer tools such as content approval, project comments and I'd guess other more modern dojo areas. Seems like a bug to me
I think I've figured it out if you read my other post, I've not got a solution yet but found the issue.
Me again, I've got this working for my case and I think it should do for you too. I've blogged about it here
Seems a bug but at least there's a work around.
Hi. We are using an external authentication provider (Azure AD B2C), which is working fine.
But when trying to "tag" a user (by typing @) in a Projects comment no users are found. The only users found are the local SQL db users that existed before adding the external authentication.
The users from AD B2C are shown if I use the "Set access rights"-tool in Admin mode, so they appear to be synced ok when a user log in.
Is this a bug, or is there something we are missing?