Why can the fields I am aiming to sync from the UI not be configured in the connector setup?
Connector: Facebook Ad Insights
Check if the required field is a part of an action breakdown, then configure the connector with that particular action breakdown selected.
For example, the action breakdown
app_custom_event.fb_mobile_complete_registration - Mobile App Registrations
offsite_conversion.fb_pixel_complete_registration - Completed Registration
Some fields are synced as part of action breakdowns.