Expand (deploy) distribution lists not working Outlook 2013 + Outlook Mac 15.9

Question

I try to figure out how to expand (deploy) the distribution lists in both Outlook 2013 (Windows) and Outlook for Mac 15 (Apple). Actually it's extremely weird because it work randomly... We mainly uses Outlook for Mac 15.9 in the Office and some people (only
a few ones) actually see a blue down-pointing arrow in from of the Distribution Lists when they are it to the "TO" field in Outlook for Mac 15.9. Then if they click on it, the list are deploying and been replaced by employees in the list. On Outlook
2013 for Windows, there's NO WAY to get the small "+" sign in front of the distribution list... FYI, the same person who can deploy on Outlook for Mac 15, can't deploy on Outlook 2013 for Windows.
I already eliminate a lack of permission somewhere in my Exchange Online manager, because I am the "owner" of distribution list and I can't expand (deploy) it anyway in Outlook 2013 and I tried to promote somewhere else as the "owner" and
it doesn't make him/her able to expand any more.
FYI I created few distribution lists in my Exchange Online admin into the "GROUP" section, they are all Dynamics Distribution Lists and as I told you, some people can deploy (well, 99.9% of peoples CAN'T deploy lists, but a few CAN do it, 0.01% of
employees).
I checked carefully in the distribution list settings on Exchange Online admin portal, but there's not much settings I can change...
The point is I MUST get the deploy feature to work with the distribution list because SEVERAL TIMES a week administration teams need to send email to all employees but while excluding a few of them, so they need to be able to deploy the dynamic list, then remove
manually the 2-3 peoples from the recipients list. As you can see on my screenshot, there's a few people where the blue arrows are working (Outlook for Mac 15.9)...

Answer 1

Hi,
Please follow these steps: -
If
RoomFinderShow = 0 under registry path: HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\Preferences
The Room Finder behaves the following ways when you start Outlook: -
The Room Finder is not shown by default on the
Appointment tab.
You can manually enable the Room Finder on the
Appointment tab.
If you open a new meeting from after enabling the Room Finder in another meeting room, the Room Finder is not shown by default on the
Appointment tab of the new meeting form.
If you manually enables and then disable the Room Finder on the
Appointment tab, nothing is written into the registry.
When you have the required update installed and
RoomFinderForceDisabled=1, Outlook will not display the Room Finder pane on either the Scheduling Assistant tab or the Appointment tab in a meeting form.
Regards
Ashish@V