I think this is a problem with the course and the change in how the submission is done.
Previously, you had to make the collection public, and I think its when the course was updated to include the private key method instead, it got broke.
I can submit the request to the old API and it produces slightly different JSON than when you submit it to the new API. Specifically, the new API brings back two apikey’s turning it into an array, breaking the test.
More details are here
Collection status: Used variables | AssertionError: expected -1 to be above -1 - Training - Postman
Perhaps this needs a support request raised?