A prerequisite to connecting Pages: Facebook Page Admin Access/ Full Control
One of the prerequisites of connecting a Facebook Page and the Instagram Page associated to the Facebook Page is to have an Admin role or Full Control.
Where can I check if I have Admin access or full control?
On Classic Pages

On the New Pages Experience
Go to Professional Dashboard > Page Access > Manage and view access. You should be able to see the Add New button under People with Facebook access. Here is a direct link to Facebook's Help center on how to Give Facebook Access for Pages in New Pages Experience.
Check via Business Manager
