You are in a Microsoft Lync Server 2013 environment.
Two distribution groups (DLs) have similar names that one DL name is a subset of the other DL name (for example, Group1 and Group11).
Both DLs are listed in the Allowed Members section under Category of the Persistent Chat page in Lync Server 2013 Control Panel.
You try to add the DL that has the shorter name (such as Group1) as a member or a manager in the Persistent Chat Room management page.
In this scenario, you receive the following error message:
Invalid members: DLName;
However, it's working fine when you add the longer one (such as Group11) as a member or a manager of the chat room.
This issue occurs because the DL that has the shorter name isn't surrounded with quotation marks.
To work around this issue, select one of the following methods:
Make sure that the DL's name is enclosed in quotation marks before you click the Check Names button and then click the Commit Changes button. For example, you have to use "Group1" instead of Group1.
Note: If you enclose the group name in quotation marks and then click the Check Names button to check the group name, the quotation marks are removed. You should have quotation marks added before you click the Commit Changes button.