Hello Stefan,
The app you are using might be v2.10 .
which requires an accurate redirect url with facebook login. We will update the plugin soon.
You can try this for now,
In the application page in facebook, navigate to Apps >Add Product > Facebook Login >Quickstart >Web > Site URL. Set the site url as your site url(which is given as a note in the plugin’s settings page).
And then navigate to Apps > Facebook Login > Settings. Set the Valid OAuth redirect URIs as the site url. And set the Use Strict Mode for Redirect URIs
as No.
And switch your Facebook app to “public”.If it still show the same issue then remove the app from the facebook account and add again.
However this message in your log is a wee bit weird, If there any such issues, the plugin wouldn’t be able to authorise the app. If you made any changes to Facebook settings that affect publishing to facebook /authorisation (after authorising the app from plugin end) then you should re-authorise the app.
If the issue persist, you can send your wp login details to https://xyzscripts.com/support/ then we can check it for you.
We will update the plugin and documentation.
Thank you for your feedback.