Welcome to the “weirdness” of the Clips APIs of Twitch. In this case it seems like a simple lower / upper case issue on the game name. If you use the “correct” game name it returns the TimTheTatman Clip:
https://api.twitch.tv/kraken/clips/top?game=Fall%20Guys&period=all&client_id=jzkbprff40iqj646a697cyrvl0zt2m6&api_version=5