So I'm out of ideas, I don't know what to check or debug anymore, but on the exception I get this:

string(188203) FacebookFacebookAuthorizationException Object

(

    [statusCode:FacebookFacebookRequestException:private] => 400

    [rawResponse:FacebookFacebookRequestException:private] => {error:{message:Error validating verification code. Please make sure your redirect_uri is identical to the one you used in the OAuth dialog request,type:OAuthException,code:100,fbtrace_id:DqCCKoiN0r4}}

    [responseData:FacebookFacebookRequestException:private] => Array

        (

            [error] => Array

                (

                    [message] => Error validating verification code. Please make sure your redirect_uri is identical to the one you used in the OAuth dialog request

                    [type] => OAuthException

                    [code] => 100

                    [fbtrace_id] => DqCCKoiN0r4

                )



        )



    [message:protected] => Error validating verification code. Please make sure your redirect_uri is identical to the one you used in the OAuth dialog request

    [string:Exception:private] => 

    [code:protected] => 100