Hands On Challenge License unavailable

I'm just knocking out some incomplete trailheads and brushing up on some skills. Currently I'm working my way through this trailhead

and in the hands on challenge, it asks me to assign the user a Salesforce license, but that isn't an option when I go to create a new user (see image).  

Closest I have is either a salesforce platform or salesforce integration license but neither of those are correct. Has anyone has this happen? How did you fix it? I'd prefer to avoid having to create a brand new sandbox, as this challenge is tied to a few other previous ones and I'd rather not repeat my work. Thanks in advance!