Hi,

I have a user in our Hong Kong office that is unable to open a distribution group she has added to her Groups. She gets the error message "Cannot perform this action, and the cause is unknown. Contact your support team to investigate."

I can add the group and expand it, so can some of her colleague, and some cannot. Her colleagues who can have the same client and global policy settings as she does. 

I read in a similar thread that this could be resolved by confirming the server times on Lync, AD (domain controller checked and Exchange but they were all correct and in sync. 

The global policy is set to 250 max contacts - but does a DL count as 1 contact, or does it count all the people within the DG? I am getting HK to confirm she does not have too many contacts but I dont think this is the issue. 

Anyone else come across this

Lync uses the Distribution List Expansion Protocol (DLX) to expand distribution lists. This protocol also specifies the web service method that is used to get the membership of a distribution list.

Look at the eventlog on the Lync server if the user try to expand the DL.

You may run also a trace on the Lync server to find out what is the problem.

Her are a little bit more details

http://designinglync.blogspot.de/2011/04/lync-address-book-service.html

You can run the command Test-CsGroupExpansion to test the ability of a user to employ group expansion.

For the usage of the command, you can check

 http://technet.microsoft.com/en-us/library/gg399009.aspx