If you're seeing KC scores appear as "0" or "-" in Long Tail Platinum, here are a few things you can try that might resolve the issue:
Make sure that the date, time and time-zone of your Operating System match your present location.
If you're still experiencing this issue, try clicking on the gear icon at the top right of the LTP window, reentering you Moz API Credentials (under 'User Accounts'), and clicking Save Moz API Credentials.
How to get SEOMoz information:
You can setup your Moz API credentials by following the instructions laid out here
If you already have a Moz account, you can check your API Credentials by clicking here and then clicking the 'Manage Mozscape API Key Button here (you'll need to Login first).
The Access ID and Secret Key from the SEOMoz page needs to be keyed in LTP.
Once done, please re-attempt to calculate Average Keyword Competition.
If you're still experiencing this issue, please contact our Support Team and we'll get back to you ASAP.