My new subdomain is not accessible

A newly created domain nearly always means it’s a DNS caching issue. Please note that using an online DNS lookup tool may not show the same IP address that your browser is connecting to. That inconsistency is precisely what DNS caching is about.

So I suggest you wait a day first and then try again.

If it still doesn’t work yet, please check this article first, which contains additional information and troubleshooting steps about that error: