When my game Subtext first launched it got like two sales in the first week. I did some advertising (free & paid) and that helped a little, but the biggest source of traffic (which brings people in to this day) was an article someone wrote about it like 8 months after it came out.
I'm not sure what kind of return you were expecting (you're not going to become a millionaire from one shooter on Itch) but don't assume that your first week will be your best one. Two years later and my weekly sales numbers are still better than they were right after launch.