Cannot create support blog

Tried to create a blog http://my domain.com/support and get error Sorry, you may not use that site name.

I checked every single section in dashboard, including banned names, everywhere one by one. I do not have a site or directory called support anywhere.

I typed the path in my browser http://my domain.com/support and http://my domain.com/support/ and get "Sorry, we can't find the content you're looking for at this URL. Please try selecting a menu item from above or to the side of this message to get where you'd like to go."

I need to create this page. Thanks for help.