Adobe Captivate 12 voices

So far I have been using a third party for generating my voice overs. However I would like to use the voice overs in Adobe Captivate 12. Sometimes I can see over 100 voices and generate them but at other times I get a message to say It appears there is a problem loading the voice. I have contacted my company's IT department - they have done various tests but they tell me that the problem is not with the security on my computer. Can you please advise?