mitel-uca-v6-micollab-client-connection-lost-will-not-connect-to-server-windows-10Version 6 of Mitel’s Unified Communications agent now called MiCollab has had troubles connecting to the MAS / MGB server on Windows 10 since the early summer of 2016.  As you can see in the screenshot to the right it displays CONNECTION LOST even though it is correctly configured and is visibly showing information from the server.

The early solutions were to uninstall some Windows Patches (KB3163018 and/or KB3172985) from June and July 2016 but that is not a comfortable solution for many.  The permanent work around is to set Diffie-Hellman encryption to 512bit in the registry:

  1. Launch REGEDIT as an admin
  2. Expand HKEY_LOCAL_MACHINE >  SYSTEM > CurrentControlSet > Control > SecurityProviders > SCHANNEL > KeyExchangeAlgorithms
  3. Right click and add a new KEY named Diffie-Hellman
  4. Right click and add a new DWORD named ClientMinKeyBitLength
  5. Set the value to 00000200 in Hex or 512 in Decimal

If you want to use a script the code is below:

Windows Registry Editor Version 5.00


If you want to download the most current Mitel MiCollab UCA desktop client, click HERE.


Mary-Ann · April 23, 2019 at 12:04 pm

I am having a similar issue and wanted to know …My company is in the USA and I am overseas trying to acces Micollab Client. I am getting connection Lost with the occasional calls connecting. Will my overseas IP address cause this?

    Ian Matthews · April 30, 2019 at 7:17 pm

    The location of either the Mitel MAS or the PC trying to use MiCollab should not be causing a problem. However, distance and number of connections can be a problem for any streaming application as there is an increased likelyhood of a break in the connection with increased distance.

SOLVED: Download The Latest Mitel Unified Communicator Advanced (UCA) Client - Up & Running Technologies Calgary · October 12, 2016 at 4:26 pm

[…] This took me quite some time to locate but in my case, UCA 6.0.422.0 worked just fine on Windows 10 Pro 64 bit AFTER I made a registry change to avoid the dreaded MiCollab CONNECTION LOST. […]

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