Does it look the screenshot below? If so, read on:
As you can see, in both the Campaign Source and Campaign Name Fields, there are two words.
However, the two words in the campaign source field are separated only by a space whereas the words in the campaign name field are separated by an underscore.
Unless words are separated with an underscore, you will get the error message shown above.
(If you have a different error message, please do email email@example.com for further support.)