Unfortunately sometimes there might be limit to the number of video ads one can watch. "No ads available" message simply means that advertising providers do not have videos available to you at the moment. The lack of ads is not a bug. During the "Ad loading" popup we try to find video ads for you and load them. If no videos were found during this time, "There are no ads available, please try again later" message appears.
Please don't worry, video ads will surely become available later and you will be able to earn bonuses for watching them.