That’s a problem with challenges. You sometimes get challenges that you can’t finish (complete a learning path if you already completed all of them, make your profile public if it is already,...).
It’s because challenges are just randomly assigned. I would use the feedback button and leave them a message. It woulb be nicer to only get challenges you can complete.
It seems your profile is already public because you page is accessible. Why do you think it is not public?
I had the same challenge and problem a couple of months ago.
I flagged it to Mendix and for me the problem was down to my profile being partially corrupted after it was ported from an old account. They did something so I wouldn’t get the challenge again, but it still left it impossible to complete until the challenges all reset again a few weeks later.