Problem:
One user cannot sign in to Skype For Business. We have tried repairing the Skype installation and clearing the Skype profile but still the user cannot login.
Solution
The below error appears if you have problems with a particular user’s AD attributes after syncing their account using Azure AD Sync and they then try to login to Skype For Business.
If we login to Office 365 as a Global Administrator go to Admin Centers and then Teams & Skype. Open the Legacy Portal and go to Users, you will see that the user trying to login does not exist.
The solution is to open ADSI edit on an on-premise domain controller by clicking Start>Run and typing adsiedit.msc. Expand the Default Naming Context and locate the problem user. Right click on the user and go to properties. Clear the following attributes:
msRTCSIP-DeploymentLocator
msRTCSIP-FederationEnabled
msRTCSIP-InternetAccessEnabled
msRTCSIP-OptionFlags
msRTCSIP-PrimaryHomeServer
msRTCSIP-PrimaryUserAddress
msRTCSIP-UserEnabled
msRTCSIP-UserPolicies
OnPremSipAddress
SipProxyAddress
SipAddress
msExchShadowProxyAddresses
proxyAddresses (Don’t clear all of these or you will break email – just remove the SIP address).
After clearing the above attributes open PowerShell on a machine with the Azure AAD Sync tools installed and run a full sync:
Start-ADSyncSyncCycle -PolicyType Initial
The user should now be able to login to Skype For Business.