WKWebView is the preferred cordova plugin for use in Cordova and Ionic hybrid applications on iOS. But Auth0’s recommended solution for cordova/hybrid applications, auth0-cordova, doesn’t work WKWebView. This ticket was opened in May and it looks like the problem has been identified:
I’m hoping someone from Auth0 can work with Max from Ionic to get this resolved. Ionic has stated that future iOS dev will focus on using WKWebView.