Scenario: You have an Exchange 2013 and Exchange 2007 Co-existence environment. Both versions are at support levels.
You are having problems managing public folders from your Exchange 2007 console or the Public Folder Management Console.
Error: Get-PublicFolder : There is no existing PublicFolder that matches the following Identity: ‘\’.
Fix: In ADSI Edit, check the HomeMDB for The System Attendant under your Exchange 2007 Server. Confirm or correct it. This needs to point to the DN of your Mailbox Database.
Repeat for your Exchange 2013 Servers. In my case, the HomeMDB was empty. I populated with the DN of a 2013 Mailbox Database for each.