In the salesforce challenge of control access to fields, I have created a permission set label: Manage Job Applications and done everything as per the challenge and the module. I have even installed the package 04t0P000000N9rs. Still I'm unable to uncheck the Candidate and Position in the field permissions in the job application in object settings. Below is the screenshot in Object manager of Job application, set field level security of candidate and position: screenshot in object manager . Below is the screenshot inside the permission set of Manage Jon Applications-object settings-Job Applications. In here after clicking edit I'm unable to deselect the Candidate and Positions fields in field permissions.Field permissions.

At the end when I tried to check the challenge getting below error:(.png)

WHAT MISTAKE I MIGHT BE DOING. PLEASE HELP ME THE SOLUTON.

Tried all the possible solutions. took help from chatgpt but still not successful in solving this case.