Healthbar greyed out

Hey so I have been trying to follow this tutorial: Unreal Engine 4 - Basic Health Bar - YouTube and it seems that I get my healthbar and it’s just grey, there’s no color fill to indicate the health percentage. alt text

Here’s a screenshot of the healthbar and the problem:

I uploaded some photos below ↓

PS. I’m new to UE4 and really need some help with this healthbar problem!
Thanks!