How to correctly set up downloading files from a subdomain?

Question

PHP

Hello!
I decided to place scripts and styles on separate subdomains script.site.ru and style.site.ru respectively.
In the header of the site I placed links like
src="http://script.site.ru/common/customscript.js"
Everything seems to be working.
But for some reason, in the 1st case out of 3, or even more often, these files are not loaded.
I can't understand what is the reason.
Perhaps it is worth somehow additionally setting up subdomains?
Thank you.

Answer 1

in the browser inspectors there is a section "Network", there
open the progress of loading the page files, see what errors when loading from subdomains