Hi Deepak,
According to my last post, I tried to generate a sample app on my personal area, including the last version of Keystore Plugin. The app was generated with success!
The original problem is:
- API 29 No longer supports com.android.credentials.UNLOCK
- You no longer need com.android.credentials.UNLOCK while dealing with API29
Please open the Key Store Plugin that you are using and confirm that you are using the correct url for the last cordova plugin. You need to have the version "2.6.8-OS4".

The last month the OS launch a new version of this plugin "2.6.8-OS5" but is not oficial, because is a beta. Try change the final part of url from "2.6.8-OS4" to "2.6.8-OS5" and generate the app.
Another thing you can do is to temporarily remove the plugin from your application and try to generate an application, to ensure that the error is caused by this plugin.
Thank you.