At this time, it is known that there is a conflict between the EIOBoard Outlook Add-in and the iCloud Outlook Add-in. When both are enabled, the Outlook Appointment tab does not appear when creating a new appointment (as seen below):
A fix for this is planned at some point in the future. For now, here are a couple of possible workarounds for you:
If you do not use the iCloud Add-In, uninstalling it will fix the issue with EIOBoard. Note that it must be uninstalled and not just disabled; if it is disabled, it will automatically re-enable itself the next time Outlook starts up.
Use the EIOBoard Browser Interface. This is a version of EIOBoard that you can use in any standard browser (such as Internet Explorer, FireFox, Google Chrome, etc.). To use this interface, log in to http://eioboard.com/eioboard/ (if you are EIOBoard-Hosted) or browse to your server (if you are Customer-Hosted).
Use the EIOBoard Stand-Alone Application. This interface is exactly the same as the Outlook Add-in. All the features are exactly the same. The only difference is that it is not integrated inside of Outlook. This is probably the easiest work around if you still want to keep iCloud installed but still keep all the features of the Outlook Add-In.