Nextend Social Login took place of the Nextend Facebook Connect, Nextend Twitter Connect and Nextend Google Connect plugins. If you had these plugins activated on your site, you can import the settings from the legacy plugins.
What happens after you upgrade to Nextend Social Login from any of the Nextend Connect plugin?
Facebook, Google and Twitter starts to work in legacy mode. In legacy mode you should be fine as the old codebase is used.
Is there a way to change the legacy mode to the new mode?
Yes, you just need to go into Nextend Social Login and click on the “Import” button. It will transfer your settings to the new mode. Legacy users will be able to log in with the new mode, too. You can check each provider specific details regarding the import: