Hi,
What you're saying is not logical. If it works for other emails of HikaShop, there is no reason it wouldn't work for that email too.
So I went in your backend, changed temporarily the "Order creation admin notifications email address" setting to my email address and then placed an order on your website. And just a few seconds later, I got the admin notification to my mailbox:
take.ms/NgNs4
So HikaShop is working perfectly fine. And no, no one else had the issue so far.
That's why I asked you to check your email address, try with another email address, etc. You can see, it works for me so HikaShop is sending the email...