Unfortunately I can not help you, but I can summarize a bit what I observed.
Itch support is swamped by a lot of things and the indexing feature of the site is seen as a secondary bonus. It's just not a priority. They want you to do your own promotion. And the game being indexed or not, does not change any promtion you would do. People would click your link, not search your game's name. (Oh, and if people would search your game's name, like so https://duckduckgo.com/?q=Sinathir&ia=web the very first result happens to be your game on Itch.)
They do have an automatic that sorts new games and even updates into two or more categories. The first category gets indexed. The other gets on a pile for human staff to look over. What influences this is intentionally kept secret. So do not expect any official answer anywhere why a game was not indexed yet, or put into quarantine. They will of course not answer any such questions per mail. Furthermore, there will not be any indication in your dashboard, about the status of the game in regard to indexing.
Intentional delisting is very rare, but it can happen. It might even be done by the automatic. There are mechanisms in place to protect against fake traffic. If they suspect a developer to cheat popularity, they might delist projects as an example. There are bound to be other reasons. But in most cases it will just be what I mentioned above: they are swamped. And maybe even misplaced the case. They do have a lot of ddos attacks and other problems. Plus, they see indexing as a bonus and not as a core feature of the site. You can even operate your game, if it is in quarantine. There is only the warning message, but the download is not blocked.
Whatever triggers the temporary delisting, it might be triggered multiple times with different updates. It might even put you at the back of the pile when you were close to be reviewed by staff. There are game that were quarantined multiple times. (Your game is not quarantined.)
From a quick glance, your game is not something that would be intentionally delisted. So the course of action is to write one mail (1) and after nothing happens for a few weeks, post it in a thread like this. The community moderator will likely forward it to staff for consideration of expedited treatment, as staff does not usually read here. The communication channel to staff is the support mail, but they typically do not answer questions about indexing. They just index the game eventually.