This is probably going to be a dumb one, but I'm going to ask anyway. Yeah, I know, never stopped me before.
After I flash an OpenWrt upgrade and install my usual packages (some of which I'm not using - I just want them there in case I later do) with no issues or warnings, I next get a lot of "Configuring [package name]" lines in my terminal window. Very occasionally after one of these lines, I get "NNNNNN WARN : Service section disabled! - TERMINATE" in my terminal session. I'm seeing it after configuration messages for the following packages: kmod-ipt-conntrack-extra and luci-app-ddns on my AP's, and iptables-mod-ipopt and ca-bundle on my EdgeRouter.
Everything I'm using and set up is working just fine. Are these warning messages just OpenWrt telling me I haven't set up the input for these packages in the configuration files yet? If so, I'll ignore and move on.
@lleachii is exactly right about this. In particular, I have noticed the ddns package producing the specific warning message. As soon as it finishes installing, it will attempt to start the service, only to find that it is not configured. Don't worry about that, though, as this is totally expected after installation. Once you configure it and start the service again, it should run (or if not, hopefully you'll get specific information about why it is unable to run).