Hi, I'm John! I will help you with this.
First, let’s make sure you’re signed in with the same Microsoft account you’ve been using to earn your streak, sometimes being signed into a different account can cause the streak to show as zero.
If everything is correct & if you don’t recall missing your streak today or yesterday, don't worry, you can actually ask the Microsoft Rewards team to help you restore your streak.
Please use this specific link with the appropriate category: https://rewards.bing.com/support?categoryId=earning_points&subcategoryId=broken_streak
I really hope they can restore your lost streak soon. In the meantime, please continue using Rewards and completing your tasks as best as you can.
I really hope this information is helpful! Let me know if you have any further questions or concerns.
Regards,
John J.D.