Grab posts by multiple categories

So I have the below code that works great:

Where in the else statement, I’m calling to pull in all posts tagged the 1 category which is working great.

Here is what I’d like to achieve – So I’m attempting to pull posts from two different categories in the else statement, but I can’t seem to make it work correctly.

Here is my attempt:

I’d like to pull in all posts from my categories tagged 9 and 3, but I’m getting no results back – but when I call get_posts_by_category, I in fact do get results back.