Please read the rules of this category, where it says that the people you're addressing are unlikely to see your post, and what to do instead. But your games are indexed.

even when searching for their exact titles or using relevant keywords

Your username is too short to search your projects by username reliably. But all your projects are indexed. Also, your username is not kupstudio, but kup. https://itch.io/search?q=kup There is at least two of your games appearing currently. But none for https://itch.io/search?q=kupstudio

Search does not work the way some people might expect it.

It is literal title search for project titles and projects by username. No keywords. And it is weighted by relevance to words and parts of words. See the relevancy of "studio" in the results above. And if you use clutter in your title like [demo] or (working title), that is very bad for the search engine, as it thinks thats part of the title. You can put those things in the short description that is displayed below the title. Of course you might still find games with literal exact title to the letter, but if you use parts, there might be too many results. There are only about 60 results.

Since no time confirmed your games are indexed an hour after your post, either they were coincidentally indexed at that time, or you could not find them in the general search maybe due to some of the reasons above. You can use a tag combination that only has a few games, to see if your games are discoverable, if general search does not list them.