On a migration recently we moved a bunch of users from Skype for Business On-Premises to Microsoft Teams Only, leaving behind Enterprise Voice users for the time being.

During this interop period it is required that both EV and Teams users can join Skype for Business meetings hosted by the remaining on-prem users until such time as Teams meetings take over.

After moving several users, reports came in that Teams Only people could not sign in to Skype for Business using the mobile app to join a Skype meeting, but where able to sign-in using the Skype desktop client.

The message received on the mobile client

Troubleshooting the issue with the old Lync Connectivity Analyzer suggested that something wasn’t quite right with the authentication process via the autodiscover web service

Autodiscover: SendRequest(): the URL https://lyncdiscover.commsverse.com/Autodiscover/AutodiscoverService.svc/root/user?originalDomain=commsverse.com?sipuri=John.Smith@commsverse.com couldn’t be connected.  Complete HTTP headers:\r\n Pragma: no-cache

I decided that I would run CLS Logging and trace the authentication, so from a Front End

Start-CsClsLogging -Pools FEPOOLA.commsverse.com -Duration 00.00:02 -Scenario Authentication

I attempted to sign in from mobile to capture some logs.

Searching the logs, top tip to reduce the export size, always specify the URI you are interested in, it makes following the log much, much easier!

Search-CsClsLogging -Pools FEPOOLA.commsverse.com -OutputFilePath c:\temp\mobile.log -Uri "john.smith@commsverse.com" -MatchAny

Opening the log in snooper and following it line by line I found that authentication passed, but the FE could not find the hosting provider for the user.

(0000000001B0CB29)Could not find hosting provider for hosted user. User: john.smith@commsverse.com

So Next step was to check the hosting provider for Skype for Business Online

Get-CsHostingProvider -Identity SkypeforBusinessOnline

Identity                  : SkypeforBusinessOnline
Name                      : SkypeforBusinessOnline
ProxyFqdn                 : sipfed.online.lync.com
VerificationLevel         : UseSourceVerification
Enabled                   : True
EnabledSharedAddressSpace : True
HostsOCSUsers             : True
IsLocal                   : False
AutodiscoverUrl           :

Missing was the Autodiscover URL for Skype Online, so setting that on the hosting provider as follows

Set-CsHostingProvider -Identity SkypeforBusinessOnline -AutodiscoverUrl https://webdir.online.lync.com/Autodiscover/AutodiscoverService.svc/root

Forcing replication of the CMS and then trying to sign in again fixed the issue and Teams Only users are able to sign in to Skype for Business Online using their mobile app successfully.

The reason why the desktop client was unaffected is because it looks up the _Sip SRV DNS record for the access edge location and redirection was happening properly through SIP registration.

So make sure you set the Autodiscover URL in your Hosting Provider for SfB Online if you want mobile sign in for those legacy meetings!