Skype for Business clients can get into a scheduled meeting, but Web App can't


I have a Standard Skype for Business pool, where the Web App doesn't work

When users access the meeting url, and don't have a Skype for Business client installed, the Web App report this error:

Sorry, that didn't work.
There was an error in contacting the service. Please contact your administrator.


If the SfB client is installed, it work as expected

This happens for both internal and remote users


Any ideas to troubleshoot this?

14 Replies

Have this worked earlier or have you always been experiencing this problem? Do you have the same problem from internet and from internal LAN? There is two different URLs that your client contacts depending on if you are internal or external.


Are you running the latest CU (CU8) on your servers? Not there is any update that should solve this in the update but it is good to have the latest update and installation of and update could fix errors.

I didn't install the SfB server so I can't say if it ever has worked

Yes, it fails both internal and external

Server is updated to 6.0.9319.537 (CU8)

Can you check in the Lync event Viewer if you see any errors when you try to open the web app?


I see this error:


Log Name:      Lync Server
Source:        LS Join Launcher Web Service
Date:          11-02-2019 06:17:56
Event ID:      64004
Task Category: (1077)
Level:         Error
Keywords:      Classic
User:          N/A
Failed to lookup Base URL This may indicate a possible configuration problem or a Fuzzing attack.
Incoming URL.
Cause: Possible configuration problem.
Make sure you have run Enable-CSComputer on all the Front End servers and Directors.  If the problem persists, check the server traces to examine the incoming URL and determine if this is a potential Fuzzing attack.

If you have changed URLs recently run Enable-CsComputer on the Front End Server, I guess you only have one?


Check that Internal web services address and External web services address are correct. Do they point internally Front End server or a Load Balancer?



Haven't change the url's

Enable-CsComputer is tired

DNS is pointing at the front-end server, no Load Balancer in this setup

Are you able to open the URL from a web browser? You should see a javascript.


Also do you see this error in event viewer every time you try to join a meeting with the web app?



Yes, I can open the url and see the Utilities.js file

I thought the 64004 error came every time i tried to join a meeting with Web App, but actually this is not the case

This means I don't see any error in the Lync Server log, when I try to join a meeting with the Web App

Was unable to find this error, and decided to install a new server :(

I think that was a good decision, you will reinstall in a couple of hours. Your other option would be to collect logs and send them here, to a Skype consultant or Microsoft Support and that might take the same amount of time (or longer).

Hi @Claus-Ole Olsen 


Did you patch the new server to the same CU level??


I have this issue at a customer, which I am working with Microsoft PSS to resolve. The workaround is a new server patched to July 2018 CU (x.534), I didn't want to patch it further in case we would meet the problem.


I will post to this thread, when we have resolved the issue.


/Kenneth ML

Hi all


My on prem SfB 2015 installation is still at July 2018 CU7 and we won't patch further than that because of the issue introduced in CU8 where UCWA clients can't connect to meetings (we have a lot of UCWA clients connecting to conferences). The recently released May 2020 update CU11 introduces a fix with transferring calls between response groups that I've been waiting a long time for, but the UCWA client problem is still listed as a known issue.


Unfortunately there's really not much information anywhere online regarding this known issue and Microsoft's workaround is to contact the third party vendor to fix. So, are we supposed to contact Apple / Google to issue a fix with Safari / Chrome to allow the web connectivity to work? There's not enough information on the issue to describe exactly what breaks and it seems a bit odd to still be an issue 18 months later. I was hoping these third party vendors would have offered a fix by now but I guess why would they when they have other conferencing tools they want to steer users to?


Has anyone here patched to the May 2020 update and tested access via UCWA that can report on what the user experience is like? Can you connect to meetings via Safari / Chrome / Edge? Can you connect via the SfB app on iOS and Android?


I don't have a test environment where I can patch to CU11 and test for myself and I'm not keen on upgrading production and rolling back if the problem still exists. Can anyone here shed some more light on this?





The problem I experienced was caused by a UCWA based MSPL script. When the ISV had updated the application the problem was resolved and participants can connect using UCWA clients.


The problem was not with the browser or the meeting app plugin, so if you don't use any 3rd party MSPL applications, I would say you're good to go.


/Kenneth ML

@Kenneth Meyer-Lassen Thanks Kenneth, that's fantastic to know! I'll go ahead with the patching then. Cheers!