Can’t display Project CPT category

Hi. I’m trying to show a sidebar list of a certain category of posts within a custom post type. An example URL that points to such a category is:

https://mysite.com/project_category/video/

However, when I use this code:

[display-posts taxonomy=”project_category” tax_term=”video”]

Nothing displays. (And yes there is a “video” category. I’ve tried “Video” as well though I didn’t think capitalization mattered…)

The “project” category is created within the Divi Builder, of which I’m using a child theme – but I did locate the code where the Projects CPT is created, and the line where it’s registered looks like this:

register_taxonomy( 'project_category', array( 'project' ), $project_category_args );

So why does my shortcode not work?

(I have been able to successfully use a Display Posts shortcode elsewhere on my site to show a different custom post type, LearnDash online courses – after locating their fairly obscure CPT taxonomy name online. So I figure it must be something simple I’m getting wrong here… but what?)

Hope someone can point me in the right direction. Thanks!