Why is ば wrong here, and only たら is correct?

Just got this review:

What it wants me to write here is させられたら. But even after reading up again on both points, I don’t understand why させられば would be incorrect. Both represent “if/then”, the only difference that I can make out for this sentence is that たら would point to a higher likeliness of it happening than ば. What am I missing here?