I had to remove this line of course:
add_action( 'xprofile_updated_profile', 'xprofile_sync_wp_profile' );
Plugin now activated. Now testing to see if it does anything…
Edit: The plugin does not derail registration, but doesn’t do anything useful either. The first_name and last_name do not show up in wp_usermeta.
Why doesn’t it work? Any suggestions very much appreciated.