Custom plugin ionic "plugin_not_installed" error

Hello,
When I am running ionic cordova platform add android
it shows:
Installing “cordova-plugin-wemsolnfctap” for android

I have followed this tutorial & exactly followed this tutorial I have same code as coded in below tutorial:
https://youtu.be/w9zYXelkl6I
https://youtu.be/Q6PaFEDonac

but still I am getting this error:
"plugin_not_installed"

can anyone guide where I am making mistake?

Screenshot_1538485809