Using AD Group in Group assignment rule doesn't work

Making a Group Assignment Rule with AD Groups doesn't work for me.

I have added client PC's to a group in AD, then in EMS I've matched that AD Group with a Group created for endpoints, which is then used in Endpoint policy, which again uses the Endpoint Profile, than is handling the deployment of the install package. Sorry if this sounds a little weird, but I'm still trying to wrap my head around the terminology to explain things. The point is - the client PC's that are in that AD group do not show up in the Endpoint group defined in EMS - thus, the client PC does not get deployed with the install package. What can be the cause of this? I don't want to manually add new PC's that are introduced to the AD - as long as it's in the right AD Group it should get the FortiClient deployed...