You may want to get access to or share access for a custom conversion. This is likely to become a bigger issue related to iOS 14 and Aggregated Event Measurement. How custom conversions are shared will depend first on how they are created.

Read my blog post on this here:

https://www.jonloomer.com/how-to-share-facebook-custom-conversions/

If you'd like to learn more about how to prepare for iOS 14, sign up for Jon's latest training at jonloomer.com/facebook-ads-ios14.