Can't access the subdomain with www

[Tsa]

I have a problem with my hosted site.

I have a domain, say, domain.com and it's fine. It can be accessed through domain(dot)com, www.egdomain(dot)com, https://egdomain(dot)com and http://egdomain(dot)com

I've made subdomains from cpanel say sub.egdomain.com
I can access them with https://sub.egdomain.com and sub.egdomain.com
But can't access it from www.sub.egdomain.com or http://sub.egdomain.com

I can't create sub domain www.sub.egdomain.com as sub.egdomain.com is already there.
I've tried 301 redirection with all the three options without a success.

The problem seems to be on the sub domain level. What could be a possible solution for it?

PS: . replaced by (dot) due to linking issue on some examples.

 

[cPanelLauren]

When you create a subdomain in cPanel it automatically adds the A record for the subdomain and a CNAME for www.sub.domain.tld you shouldn't need to do anything for www.sub.domain.tld. What happens when you try to access www.sub.domain.tld or when you attempt to access http://sub.domain.tld?

 

[Tsa]

Both of www.sub.domain.tld and http://sub.domain.tld seems to redirect to https://www.sub.domain.tld (https://www.domain.ltd works)
And Firefox shows an Corrupted Content Error.
The page you are trying to view cannot be shown because an error in the data transmission was detected.

And for chrome it's ERR_INVALID_REDIRECT.
All my redirect settings are deleted for over 24 hours now (all of my domain and subdomain .htaccess files are empty).

 

[cPanelLauren]

Do you have a CMS installation on the subdomain? That is the only other method that could be redirecting the domain.

 

[Tsa]

Yes. I have different CMS installed on my sub domain/s while my domain has a different one.

And I'm sorry to bother you all with my stupidity. It was my CMS that was disallowing the www. It was just in the settings of my CMS.

The issue is solved now.