Where is Addon Manager for P3D4?

[Sploosh]

I am installing onto a new computer. I cannot find the download for Addon Manager for P3D4. AND, the installers for the airports don't include P3D4, saying it isn't supported.

[virtuali]

http://www.fsdreamteam.com/products_addonmanager.html

Since 2017, with the new Live Update system, the FSX/P3D version of the Stand-Alone Addon Manager is not required anymore, since the Live Update program can keep all FSDT products which are currently installed, always updated.

AND, the installers for the airports don't include P3D4, saying it isn't supported

That's because your P3D4 is outdated. Our products requires 4.4 at least. I suspect you have old installers, since all the new installers don't just say "not supported", but the text indicates your current version, with an indication that explains the installer cannot proceed, because your version is too old.