Why doesn't Facebook's "conversion" ad optimization option work?

Question

Facebook

Hello.
I can't figure out what I'm doing wrong when setting up ads on Facebook1 I'm setting it up
through the business manager. Selected the goal of "conversion". I created a pixel, installed it on the site, set up events in the event manager, when I create an ad, when I select the "conversion" goal, nowhere is it asked what is considered a conversion. Further, in the ad group settings, in the "optimization" section, the "conversions" option is simply not active. What is the reason?

Answer 1

Same problem, tinkered for 2 days.
What helped:
1. Validation of the domain
2. in Events Manager-> Data Sources,
you need to configure the "measurement based on aggregated event data" tab

Answer 2

In the ad group, there you need to specify the pixelb and the event of which the conversion will be considered. Which one did you indicate?