Can't see users on the groups I just import from AD.

encountered this as well but the "had to login into user portal so the XG can cache their credentials."  did the trick for me.

but i did not logon all users in the portal, only those users who are not synced.

The users are created on XG, when they authenticate successfully.

At the login, the group memberships from AD are retrieved.

https://community.sophos.com/kb/en-us/123161

May also help you to understand the group membership behavior on XG.

So, I have another question about this...

If my users change their password, they should login in the User Portal again?

Even if I have STAS configured? Or I'm misunderstanding whats STAS for?

Thanks!

I am not quite sure if i understand your question correctly.

But remember: The user is created or updated on the XG when the user authenticates on the XG.

It does not matter which engine authenticates the user (User Portal, STAS login, SSO Client, Captive Portal, etc.). 

You will not have to re-login to the user portal when the user updated his password, because it will be done automatically when the user authenticates again.

If you are using STAS, the user is authenticated on XG when the Collector send this event to the XG (Login Event, or WMI Polling).

Thats exactly what I need to know,

Thank you very much.