Have had this problem as well, several people have made threads about this problem and they seem to be ignored.
It's always the FIRST video to load after clicking "Earn Crowns", it has a blank black background with a Play button in the centre and the words "Powered by Supersonic" in the upper right. When you click on the play button it goes to a screen that says "Sorry, something went wrong with this video. Please try again" but there is no way to try again, it just fails.
Usually I only get 1 other video before it says I am out of ads and returns me to the game. If I try a few hours later, it's the same broken video FIRST, then either it runs out of ads, or there's one other video (usually working fine) then it's run out again.
Please take this up with your third party ad service, as it's been this way for a MONTH. I'm sure there are plenty of games wanting ad space that aren't getting there because the app is busted or there's a glitchy one in there.
This feature hasn't worked correctly for me since shortly after it was first implemented. Recently I've been having that same issue where it says something went wrong with the video and then usually it'll say its out of ads. OR if the video actually does work, then I'll get the message saying that the crowns are on their way to my account and that it could take a few days for them to arrive, but they never do. I haven't bothered to contact customer service about this since I would literally be emailing them every few days asking for the crowns I earned but was never given. Rarely do I get a video that both plays all the way through AND actually gives me my crowns immediately after watching.
I have had the same problem i just need 100 crowns to stitch something and i don't want to spend money to get 2400 over i just wanted 100 but now i cant get anything through PLEASE PLEASE fix this kingsisle