We understand it's disappointing to spend time completing the Rewarded Challenges, only to get nothing in return but here could be some reasons why you did not receive your reward:
You did not watch the Watch & Win video until the end or you might have closed the video prematurely and invalidated your challenge.
You did not answer the question after a Watch & Win video correctly.
You did not complete an Answer & Win challenge or answered one or more questions incorrectly.
You have already completed the challenge before.
Your internet or network was unstable. Please check your connection and try the challenge again.
If you have completed a Rewarded Challenge but still did not receive the reward, please wait for a few seconds as there might just be a slight delay between the end of the Rewarded Challenge and the reward being given.