Making Fire and Lava do Half the damage

i have a potion effect that makes it so players take half the damage from fire and lava. but i cant get it to work.


https://imgur.com/a/SmcwEhN

here is the procedure i have, its not optimized i was just trying to get it to do anything,

i had put some debug markers in it to see what wasnt activating, and the part that isnt activating is the "provided damage source" part, even if i had been fully submerged in lava or fire it would not activate.

help would be greatly appreciated!!