Welcome to the Make community!
You inserted an absolute (full) URL into the URL field.
If you read the description below it, it says:
Enter a path relative to https://__________ … For example: __________
So you simply need to OMIT the first part of the URL that will be added for you.
/v1/mixed_people/search
Hope this helps! Let me know if there are any further questions or issues. P.S.: investing some effort into the tutorials in the Make Academy will save you lots of time and frustration using Make!
— @samliew