Can't save dropdown or checkbuttons to custom taxonomy

I’m trying to create a custom post type from a ‘gravity form’ and ‘gravity form + custom post type’ form. I also want to add the post to several terms of two custom taxonomies. I added two questions to the form to determine which terms I should add the post to. One is a dropdown, only one option possible; the other is a checkbox, multiple options possible. These questions are populated by the respective taxonomies.

I can create the post of the custom post type. It doesn’t safe the post to any taxonomie terms however. How should I achieve this?

https://www.ads-software.com/plugins/gravity-forms-custom-post-types/