what I need to do to restore normal search visibility
Wait and ignore.
One of your games is in quarantine. Two are indexed. And three have payments active and are nsfw and Itch delisted all such games last year.
Viewing post in Why was my game placed in quarantine?
I do not know. Since they did not tell you, I would igore it and update and work on the project like you would without knowing that it is in quarantine.
Maybe this has answers for you.
https://itch.io/t/4120453/unofficial-search-and-indexing-faq