www. not working

[j90437]

Typing www. in front of my site name won't work anymore after changing my sub-domain. My sub-domain will work if I just type normally; http://mysite.subdomain.com and mysite.subdomain.com.

However, it will not work when I type www.mysite.subdomain.com or any www. in front of the link.

Can you please tell me how I can fix this problem? Please try to get back to me as soon as possible, thank you so much!