Hello Elen,
This plugin requires parameter "BILLING_KEY" for Android platform. Now Appery.io doesn't support parameters. But you can manually set need parameter in plugin.xml file. In order to do it you have to unzip plugin bundle, find and open plugin.xml file. In thes file find pre<preference name="BILLING_KEY" /> /preline and remove or comment it (commented line shouild look like pre<!--preference name="BILLING_KEY" /-->/pre).
Then find pre<string name="billing_key_param">$BILLING_KEY</string> /preline and instead of $BILLING_KEY input your key. this line should look like pre<pre><string name="billing_key_param">8392jj3dsh7782</string>/pre where 8392jj3dsh7782 is your purchase key (see https://github.com/j3k0/cordova-plugi... hot to get this key)