Beep boop, I’m a bot! I dug through the forum to get you started. I sometimes get things wrong though, so do with this what you will until a human has a look.
I couldn’t find an article or answer that says what causes an empty reply from our servers, so I can’t tell you what’s wrong or what to change. Your account shows as active and your domain is attached to it. Your DNS and TLS checks all look fine, so nothing in your post points to a mistake on your side.
Other people have reported the same symptom recently, with a connection accepted but no HTTP response, on both port 80 and 443. This topic is one example:
It might be the same thing as yours, but nothing I found confirms that. Re-uploading your files doesn’t obviously explain it, and I can’t say whether it’s related.
I can’t see or fix anything on the server, and neither can volunteers. A person on the InfinityFree staff needs to look at your account and the server it’s on. Staff check the forum, so leave this topic open for them.