Skype for Business Mac client 'We couldn't send this message'

[Marco Schilder]

We're using an on-premises Skype for Business environment, when Windows or Mac clients try to send a message to a Skype for Business Mac client, the sender usually receives 'We couldn't send this message' while the message is delivered. It probably has something to do with the Mac client not confirming/ not being able to confirm the arrival of the message to the Front-End server. I also noticed that the Skype for Business iOS client states that Push notifications are not supported, while this is enabled on the server.

I have checked the Push notification settings and tested if they are correctly working using Test-CsMcxPushNotification, no errors shown there. The Mac client is already installed on a clean installed Mac.

Skype for Business Mac client: 16.6.333

Skype for Business server: 6.0.9139.0

Any suggestions?

[#2]

This was resolved for us by changing the following parameter in the voice policy assigned to both the sender and recipient of the IM: IMLatencyErrorThreshold We set this to 20 minutes, the value itself is expressed as milliseconds. https://technet.microsoft.com/en-us/library/gg398300.aspx

[#3]

Sorry I meant to say CLIENT policy, not voice.

[#4]

Thank you! I recently updates to:

SfB Server: 6.0.9319.281

Mac client: 16.7.191

That solved the push support for iOS, it also 'seems' to solve the subject of this issue as I have not gotten any complaints yet. I'll keep you guys posted.

[#5]

I haven't had a lot of time to be busy with this issue, but unfortunately it hasn't been solved yet. It still feels like some kind of firewall issue since the Mac clients uses Skype EWS and the Windows client Skype SIP (for what I know?) That also explains the same behavior on mobile clients, these clients are not able to reply for the successfully received message.

[#6]

It seems to down scale the number of warnings we get, but not all :(