There are several reasons why users may not appear in the user list:

  • Users are not licensed
  • Users have calling plan

To get more information, view the most recent Sync history from the drop down on the Sync Now button:

Users are not licensed

If in the Sync log you see information like this:

<00:00> GRAPH> Enabled users: total=15, licensed=13, phoneSystem=0, excludedByCallingPlan=0, resource=0
<00:00> GRAPH> Found 0 users with a Phone System licence (none have a Calling Plan)

Then 0 users have the correct Microsoft licenses for the Teams service.

Refer to this article regarding Microsoft user licencing:

For testing and quick setup you can apply the Common Area Phone free trial to users:

Users with calling plans are excluded from the Sync Now process.

If in the Sync log a message like this can be seen:
<00:01> GRAPH> Enabled users: total=399, licensed=127, phoneSystem=108, excludedByCallingPlan=104, resource=0
<00:01> GRAPH> Found 108 users with a Phone System licence, of which 104 are excluded as they have a Calling Plan

Then this is why the users are not in the Add User list.

We advise going into the user's licence on Office 365 and removing the 'Calling Plan' (may say Domestic or International)  and running Sync Now again.

Note if users have  ‘Communications Credit’  added to thier account, this has the same effect as a calling plan, so should be removed to make the user appear in the Add Users list.

Access this licence in the Office 365 portal for the affected users:

If the Calling Plan is not shown in this list then it may be part of a bundle SKU ans will sit in the Apps list further down the licence window above

Remove the Calling Plan, the user will then not be excluded and will appear in the list.

Press Sync Now to bring these users to the portal for setup

Calling plans are where Microsoft is providing the phone number and minutes, so probably not wanted here anyway as that's what the Call2Teams service provides using the customer's existing phone services.