Did Sorry for the inconvenience, Sketchub is currently using Admob services for monetizing the app, but our Admob account serving is limited and because of it, it is unable to load "Video Reward Ad". The error may last for few more weeks before Admob resolves problem with our account. We really understand the problem you are facing and we are working our best to bring the feature back as soon as possible.
However, the alternative way to tackle this problem is to get a premium plan for your account (which can be currently obtained by donating small amount of money).