This package aad_oauth has a dependency name flutter_secure_storage And flutter_secure_storage have a native method name delete

So I guess when you use oauth.login() or oauth.getAccessToken(), the native method delete will be called, but somehow in native code, this method didn't exist, that's why you got the error

MissingPluginException(No implementation found for method delete on channel plugins.it_nomads.com/flutter_secure_storage)

So let's search keyword to check whether your project downloaded the dependency success

Native method "delete" on Android:

on iOS:

If your project doesn't have them, you may try clean flutter or pub cache, then re-sync the dependencies.