Do you see any errors in your browser console? We have the same plugin version installed on this forum (2.5.2) saving the settings on that page works fine.
What does this give you when you run it in nodebb folder? npm ls nodebb-plugin-sso-google? Also try stopping nodebb and running ./nodebb build then try loading the plugin page again. If the client side files are built successfully you should see the sso-google file loaded like so