Free gems are awesome! Our team knows that and we try and provide a healthy balance of free diamonds throughout our different game modes. One of the best ways to accumulate diamonds for free is by voluntarily watching video ads.
However, this isn't an infinite source of diamonds, and there might be times when the button becomes unavailable:
1) Everyone has a limit of videos to watch per day. Once you've exceeded this limit, you'll need to wait until the next day before you can watch more video ads.
2) It is possible to run out of videos from our third-party video ads provider. Video ad availability depend on a few things, such as your country and device's privacy settings. In this case, you'll need to either wait until more videos are available to you, or change your device's privacy settings.
3) There is a lifetime limit of video ads each account can watch. Once your account has exceeded this limit, you won't be eligible to watch video ads anymore.
If your video ads button is unavailable due to one of the reasons above and you would like to find out more ways to earn diamonds, please refer to this article.