[Sjn]

Well, you probably didn't update the prograssbar's value with the player's health.

A timer would be needed to keep updating the bar value depending on player's health.

Example;

Code:

new Float: health;

GetPlayerHealth(playerid, health);
SetProgressBarValue(barid, health);

And btw, try not to create a bar id with "health" name, you may create another variable calling it "health" in the future. It will give you an error.