wpmudev ultimate-facebook under registration

Hi there i’ve installed in my wp plugin reading following topic: https://wpgeodirectory.com/support/topic/adding-facebook-signuplogin-plugin/

I try the stiofan fix

add_action( 'social_connect_form' , 'wsl_render_auth_widget_in_wp_login_form' );

to add button on register form also but on my register box instead of the button i got:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wsl_render_auth_widget_in_wp_login_form' not found or invalid function name in /home/content/79/9084479/html/findercoach.com/wp-includes/class-wp-hook.php on line 298

any help to fix that?
thanks in advance
Valdo