Ask HN: Best way to do coding screens?

Our interview process is fairly quick: 1. 15 minute phone call 2. 30 minute coding challenge on zoom 3. Paid onsite

What we’re struggling with is many people are passing the first phone call and then completely flipping the coding challenge. Many of the applicants don’t know how to code. These are people with 5+ years of experience as a software engineer.

How do you structure your interview process to maximize the time you’re spending talking to qualified applicants?