Trying to set up a site as an addon domain before moving it from another hosting account? You may get mooned by cPanel in such cases. Here is there error you see and (more importantly) how to fix it.
When you try to set up the addon, you get this message:
There was a problem creating the addondomain. Show Details
Error from park wrapper: Using nameservers with the following IPs: xx.xxx.xxx.xxx,xx.xxx.xxx.xxx Sorry, the domain is already pointed to an IP address that does not appear to use DNS servers associated with this server. Please transfer the domain to this servers nameservers or have your administrator add one of its nameservers to /etc/ips.remotedns and make the proper A entries on that remote nameserver.
In order to eliminate this error, go into WHM. In Server Configuration, under Tweak Settings option, check this box:
Allow Creation of Parked/Addon Domains that resolve to other servers (i.e. domain transfers) [This can be a major security problem. If you must have it enabled, be sure to not allow users to park common internet domains.]
Once you’ve created the addon domain, you can untick this box again. It’s more secure to leave it unchecked, of course, but many times you’ll want to get the new site up and running before you change over DNS, huh? At least, if you’re smart, you do.
photo credit: bwright923

This helped a LOT. Thank you.
You’re welcome.
Man, I had no idea how many settings there are in this Tweak Settings thingy. I’ve always looked to change options in the cPanel, not the WebHostManager. I can do things here I used to write to the support to fix, lol.
You can also park from within WHM and it does not have this restriction.
Thanks for the tip, Steve.