Hi @jfoc
In the debug mode we only try to check if your server is able to communicate with the servers of the provider, to do this we send a text request, and we dump out the response. All that matters there is if you receive the Network connection successful message at the top of the page or not, everything else are just the verbose text of the API response, so you can ignore that. I do not know if your message says the connection is successful, as you included only the error message part, but if you see “Network connection successful *” notice at the top, then you do not need to worry about this debug mode.
You mentioned all settings are verified, so if you haven’t done already, please enable the provider, and you can check it on the /wp-login.php page whether the login with the social button works or not. If it doesn’t, let me know what error you get.
And if you would like to publish the buttons somewhere else, in the Free version you can use the shortcode for that:
https://nextendweb.com/nextend-social-login-docs/usage/