Content mismatch.
THE COMMON CAUSES
Wrong document root The domain not actually pointing here A conflicting alias or subdomain Caching
CHECK THE DOCUMENT ROOT
cPanel, Domains. Each domain shows its root.
If two domains share a root, they show the same site.
CHECK WHERE THE DOMAIN POINTS
Look it up. Does it resolve to your server's address?
If it resolves elsewhere, you are seeing another server's content.
IF IT SHOWS YOUR MAIN SITE
Either the document root is public_html, or the domain was added as an alias rather than an addon.
Check which.
IF IT SHOWS A DEFAULT PAGE
The domain resolves to the server but is not configured on your account.
IF IT SHOWS ANOTHER CUSTOMER'S SITE
The domain points at a shared address and is not configured here.
Add it to your account.
AFTER FIXING
Clear any caching and test in a private window.