There is a difference between being an Admin or having Full Control on a Facebook Page (= administering Facebook Page) and being an Admin or having Full Control on a Facebook Ad Account (= administering Ad Account).
Admin on Facebook Page
If you are using Business Manager, you can check on which Facebook Pages you are Admin by following these steps:
Select the correct Business Account
Select Settings
Under Users select People
Choose your name
You can check your role(s) on the right side
Admin on Facebook Ad Account
If you are using Business Manager, you can check whether you are Admin on a given Ad Account by following these steps:
Under Accounts select Ad accounts
Choose the corresponding ad account
Click on the Ad account access tab
Make sure you're listed among the people managing the given ad account
Important: Please note that in order to configure your Facebook Ad Account in Agorapulse (to have your ad comments synced), you need to have the role Advertiser or above (Classic Page) or Partial Access with Manage Campaign permission enabled (New Page Experience) on the Ad Account. Having a role (even Admin/Full Control) on the Facebook Page is not enough.