Are you trying to add your Facebook page(s) but can't select the correct page(s)? This is how you solve it:
When you registered your Facebook page you came to this screen (blue text: 'Choose what you allow':
Here are probably not all pages set on 'Choose what you allow'. To fix this you can go to this page and remove LinkPizza this way (1. check / 2. click):
If you then try to register a channel again via LinkPizza and the screen to allow you to manage your pages appears, it is important to click "Choose what you allow" and check all the pages.