App Not Setup: This app is still in development mode (no it's not, it's public and all lights are green), and you don't have access to it (why not? I'm the admin.). Switch to a registered test user (huh?) or ask an app admin for permissions (I am the admin).

So what is throwing this?

I can get a token on the page below....but I only get a never-ending load spinner on the site front end
https://developers.facebook.com/tools/accesstoken/

make sure you made it public at last step of app creation in doc. I will be looking at this problem on day time soon.

see img - looks public to me

I just retraced all steps and it happened again. This is a bug so I am going to have to try something else.

Update: you need to add something to your documentation. To wit: