No Custom Fields at all?!

Found these articles and tried the codes:

https://www.ads-software.com/support/topic/custom-fields-in-registration-form-2/

https://nextendweb.com/nextend-social-login-docs/backend-developer/#custom-fields

My Setup: WP 6.2, Blocksy Theme + Premium, Nextend Free Version.

I mean Facebook and Twitter Login basically work. I hit the buttons and being logged in. But i expected the Plugin is stopping me from logging in because “favorite_color” is missing. All i want to do is to ask for more fields / values. I am the only user of the wp site at the moment. What do i miss ? Placed the code example in functions.php

or does it not work because i am a already registered user? is there a kind of build in cache i need to purge?