IMPORTANT NOTE: All pages where a conversion takes place have to be a page on a domain you own and you have verified. It's not enough to just verify the domain you are sending traffic to (i.e. your registration/sales page). For example, if you're running ads to a webinar, the page people see AFTER they register, MUST ALSO be a page on a domain you own and verified inside of Facebook, in addition to the registration page itself. This means if you're running ads to an SLO offer, where multiple conversions take place, i.e. SLO sale, OTO sale, those pages where the conversion happens, must also be on a domain you have verified. In essence, ANY PAGE where a conversion takes place, must be on a domain you own and have verified inside of Facebook.