Hey Zoobster! Free gems are awesome, right?
When the button is available, you can use it as much as you want and get lots of gems to spend however you see fit in the game.
However, unfortunately, there are times where there are no vides available. This happens because our videos are provided by a third-party company and, at some point and depending on their parameters like devices and user's geolocation, they may run out of videos to show you.
But don't you worry! The providers continuously add videos, so you'll certainly get more opportunities to get more currencies!