Sometimes, when something odd happens to your server (most of the time intentionally, though not in an ideal situation) when you go to add an IP address to your server, you’ll see this error:
$IPADDRESS is already an active IP. Skipping $IPADDRESS .. already added !
And then when you check the cPanel logs (because you’re a good admin like that), you’ll see this error:
[2013-10-26 15:21:41 -0500] info [xml-api] $IPADDRESS is already an active IP. [addips] version .
Well, when that happens there are a plethera of things to check and correct. Hopefully one of these will fix it for you.