IX Workplace for Mac works great.
You need an OfficeWorker license. PowerUser is only required for using IX Workplace on mobile devices (IOS/Android)
As for external calls not completing, check to make sure the number is being sent properly.
Do you require 9 to get an outside line?
Check this..
Open IX Workplaces on your Mac.
Open IX Workplaces Preferences
Click Advanced
Turn on Dial Rules, and fill in the fields properly.
Travis