Unity 7.0 lost the connection to your message store. Check to make sure Exchange is running correctly (Your message store) on your network. Unity will take messages while the message store is offline or unreachable. It will not be able to play messages until the store is reconnected.
Can you check the Eventvwr on the Unity 7.0 server.
Also, have you made any changes to Exchange or rebooted, etc.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.