Remember that it's not the hosting account that's lagging behind, it's the domain name. It's completely standard, and always happens like this. As you've been advised, 24-72 hours is just how long it can take.
The way that it works is that there's DNS servers around the world that cache the settings for every domain name that they know about. These servers tell enquiries where they need to go to, so if there isn't a setting for an address, then the server can't tell the request where i tshould be routed to. When a domain name is added or changed these DNS servers don't instantly get the details. They update their records anywhere from a few minutes to a few days, so it depends on how these servers are configured all around the world that will influence how long it takes.
All that I can say is jsut be patient. It will work, and you will be able to get in, it will just take a bit more time.