if you are talking about the iphone/ ipad app, here is a slightly edited quote from another thread:
If you have purchased render credits or the in-app option for unlimited video rendering to your camera roll and that option does not show, "there is a 'restore
purchases' button on the page where you confirm to buy more so if you
have credits outstanding click that and the App will check in with Apple
and add anything that has not sync'd correctly."
Hope that helps,