I'm a FusionAuth employee and saw this come up.
It looks like you have
nodebb-plugin-sso-oauth installed, but from the github page, it looks like this is not a fully functioning plugin:
"Please note that this is not a complete plugin, but merely a skeleton with which you can create your own OAuth SSO plugin for NodeBB (and hopefully share it with others!)"
It looks like you configured
library.js as mentioned in the github readme? Can your share those settings changes (with anything secret obscured, of course)? Just want to make sure the config is set up correctly.
An alternative to try would be the fusionauth nodebb plugin, but it sounds like you really want the SSO plugin to work since you're planning to go to production against 10duke.