As a beginner in ionic / Cordova, I had the same problem. It seems that when you add a plugin, it need to be installed in the platform also.
I solved it to remove platform and add it again.
ionic platform rm ios
Ionic platform add ios
but it creates other problems, losing customized icons and splash screens in the platform.
One can consider using hooks
I had the same problem with the SplashScreen plugin and solved by removing the Plugin’s files in Xcode, then re-adding the plugin via cordova plugin add.
This way I hadn’t to remove and add again the platform, keeping icons and splash screens.
I solved the problem of icons and splashes by created a shell script that sets up my project and makes sure that all the plugins and OSs are installed, then it add the icons and splashes to the correct places before running
cordova build
So now I just run buildCordova.sh and it sets up everything and builds for me. My boss is a big fan of being able to do a pull, run one script and have everything working. It is a nice practice to follow
Build cordova calls setup and then for us it applies a patch for an iOS problem we had. If anyone has any other ideas for this please feel free to share