Problems with MultiSite Domain mapping

I'm having problems getting domain mapping to work.

I'm not sure I fully understand the written documentation.

The main site is a multisite install.

I want to map to

Both and are hosting on my clients GoDaddy account.

I've gone into the DNS and set an A record for to point to the IP of

I've gone into the site and set the domain mapping to

It's not working. It's still pointing to the old website. Did I miss something?