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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.
Is there a list of Alexa Skill developers? A developer registry (Companies and freelance)
Alexa Private skills in Alexa companion app