On Discourse, you need the following settings:
enable_discourse_connect-
discourse_connect_url(should be set to your WordPress site’s homepage) -
discourse_connect_secret(make sure it’s value matches what you have entered in the DiscourseConnect Secret Key setting on your WordPress site)
You should probably also enable the verbose_discourse_connect_logging site setting on Discourse. With that setting enabled you may get some useful details about the cause of the issue in your Discourse error logs.
On WordPress, make sure you’ve filled in the DiscourseConnect Secret Key setting. The only other setting that has to be enabled on WordPress is the Enable DiscourseConnect Provider setting.