Could be so, though it doesn’t look like a site where the devs have a fixed time schedule. (Not that I know much about managing a website, just my impression.)

Nope. I actually tried using a proxy and it got rejected for that very reason (with a different message), whereas two normal IPs had the problem described in OP.

My suspicion was correct, I can’t figure it out.

I know, as I’ve said, I’ve sent them an email through that form two days ago but have still gotten no response.

No, I have no idea what that is and I suspect I won’t be able to figure it out, but I can give it a try.