Problem:
I am trying to translate theme strings, but I can't register any. It doesn't matter if I try to do it with function like do_action( 'wpml_register_single_string', 'stegu', 'enter_search_terms', 'Enter search terms' ); or simply using __ . Also, options text fields page from ACF options page can't be translated (it works for acf fields in posts or pages). Link to a page where the issue can be seen: https://test.stegu.pl/
Solution:
For some reasons some of icl tables had positions with id 0. after removing them all works as a charm.
