Admob Free TypeError: Object(...) is not a function

I use Admob Free on my Ionic 3 app and it worked fine until recently, after upgrading to the latest version of Admob Free, and now ads aren’t showing at all (test mode or not). Debugging it shows that the line

this.admobFree.banner.config(bannerConfig);

causes the error

TypeError: Object(…) is not a function

Anyone have any idea why the sudden error?
After upgrading, I had to add ‘/ngx’ to the import, so it now reads

import { AdMobFree, AdMobFreeBannerConfig, AdMobFreeInterstitialConfig } from '@ionic-native/admob-free/ngx';

Any help will be greatly appreciated, as the app has been launched in the app store with no ads showing!

I ended up downgrading admobfree to an earlier version (0.21.0) and the error stopped. So is the latest admobfree plugin not compatible with Ionic 3?