Call2Teams - Customer
This error occurs because the user is set on the portal to be DirSynced.
What It Means
The customer has an on-premise Active Directory and is using Microsoft DirSync to sync their users into their Office 365 Azure AD.
If any of those users have the msRTCSip-line attribute set in their on-premise Azure AD then we will be unable to apply a phone number using the background PowerShell script, until they have cleared this attribute and run another sync to Office 365 Azure AD.
If we detect this error when doing a Call2Teams sync then we will show advice to this effect below the sync button.
However we also display that the user is DirSync'd, as shown above, to aid in troubleshooting and to help the customer avoid having aforementioned error.
What if the attribute is not set or I cannot amend it?
If the on-prem servers were removed before the attribute was removed, it can leave a flag set that cannot then be reset through the User interface or by PowerShell. See this MS article in relation to this: Managing Attributes After Decommissioning
Another solution might be to remove the assigned number from the user before adding it back in via our portal. The process for assigning/removing numbers using PowerShell is here: Updating a User's Number
If this doesn't help, you may need to report the issue to Microsoft and request they remove the attributes.
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