I am very, very, very familiar with the Enterprise Vault Outlook Add-in, but, not so much the Enterprise Vault Add-in for Mac OSX. I'm getting there with it, but I've not really had to troubleshoot any issues (which is a good thing, perhaps!?!).
One of the things that you always, always, always need to do is to look at the log file which is produced (either by the OSX Add-in or the Windows + Outlook Add-in).
To do this on a Mac, you can do the following :
Click on Spotlight
Search for Console
Click it to open it
Click on File -> Open, and in the drop down list of locations, choose Logs
Highlight and select the Enterprise Vault log file
Or you can navigate to the following location in Finder:
Open the EnterpriseVault.log file (in TextEdit, for example)
(You have to ensure you have show-hidden-files enabled to be able to get into it this second way)