Working with custom taxonomies / custom fields programmatically

Hello:
I’ve created several custom post types with custom fields and custom taxonomies in Pods. Now I’d like to manage them programmatically. At this point, I know how to create new instances of a custom post type with wp_insert_post, but I’m struggling to make wp_set_object_terms work. I expected the latter to be a very straightforward operation: wp_set_object_terms( $post_id, $tag, $taxonomy) and you’re done, but it turns out that no terms are assigned this way. My question is whether Pods (custom taxonomies and custom fields, in particular) call for some non-standard functions that are shipped with the Pods plugin, or is the origin of such custom entities irrelevant and I can handle them by means of standard WordPress functions. Thank you in advance for the clarification.