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Are you trying to do account linking? Have you followed the guide here?
Yes I have followed that guide and run this example, just changed Product_id & api_key as described there and run the app but after amazon login getting this error.
We have a useful guide for debugging account linking related issues here, though I'd double check you did everything in that guide correctly first.
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Android Application for Alexa: Not able to fetch custom skills
alexaVoiceTest app - Alexa Skill, how to enable the skill in my device?
Amazon account linking on the Android Alexa app.
Can we see how many users enabled our own alexa skill?
Alexa Private skills in Alexa companion app