It seems the error message may be due to the unavailability of the cordova-plugin-safariviewcontroller . Please make sure that you followed all the necessary steps to install that plugin.
Auth0 uses auth0-cordova plugin which in turn requires:
cordova-plugin-safariviewcontroller
cordova-plugin-customurlscheme
All these require you to run the ionic app in your device or emulator if you want to test the login functionality.
Interestingly, it is not throwing this error everytime in my android app. But like once in ten times, after building it, it throws this error randomly. I am not able to rectify the problem. I have to uninstall the app, build it again and install it, and then it works fine. But it is really annoying and time consuming to repeat the process.
I hope this information helps you to dig into the problem.
Thanks again for your time!