Correcting my own reply above: that checkbox is probably not your answer, and I should not have led with it.
I widened the check to 11 itch project pages. Every page carrying the noindex tag also served itch's quarantine interstitial instead of the file; every page without the tag handed the file over with no interstitial — 6 of 6 where a file row existed to test. Two other recently created accounts in that sample carry neither, so this is not simply "your account is new".
That fits itch's quality guidelines rather than a setting you chose: "our systems or a site moderator may choose to remove your page from itch.io's discovery index. Your page will still be accessible via direct access to anyone with the URL, or through your profile page, but ... it will not be shown on our listings."
Still look at the box, it costs 30 seconds. If it is already unticked, the Creator FAQ points elsewhere: "We put some limits on new accounts to prevent abuse. We can disable them by request, all you have to do is contact us." That means contacting itch support, not editing your page.