Strange behaviour when loading our WPMU website without www.

When I try to load our website with (www.) before the domain name the home page of our website loads normally, but when I try to remove the (www.) form the URL for example write http://domain-name.tld I always find myself routed to the signup page automatically!!

I’ve tried searching to see if someone else is facing the same problem but couldn’t find anything :slight_frown:

So can someone please tell me what I might be doing wrong here?

Thanks in advance for your time