Alexa Skill Account Linking Issue – First Time Worked, Now Failing

Based on your description, this is a common issue with Alexa skill account linking. Since it worked the first time but fails on subsequent attempts, there are several potential causes to investigate:

1. Token validation issues: Your token response structure appears correct (with access_token, refresh_token, token_type, and expires_in), but there might be issues with how tokens are being validated or refreshed on subsequent attempts.

2. Browser or network issues: Try clearing your browser cache and cookies, using incognito/private mode, or trying a different browser or network connection.

3. Token endpoint accessibility: Verify that your token endpoint remains publicly accessible and is responding correctly to requests from Alexa's servers.

4. Refresh token handling: The issue might be related to how refresh tokens are being processed. Make sure your authentication server properly accepts and processes refresh token requests.

5. Token format: Ensure there are no extra spaces, special characters, or formatting issues in your token response. Check that your Content-Type header is correctly set to application/json.

6. Permissions configuration: Double-check the "Permissions" section in your Alexa skill configuration to ensure that all required permissions for account linking are enabled.

7. Skill configuration: Verify that your skill's account linking configuration in the Alexa Developer Console exactly matches your authentication service settings, including authorization URL, token URL, client ID, and client secret.

If you're testing in development mode, ensure that your development endpoints remain publicly accessible and that all security certificates are valid. Checking your server logs during the account linking attempt might provide more insight into what's failing during the process.
Sources
Unable to link Alexa skill with my mobile application in AWS (Dev mode testing) | AWS re:Post
Unable to link Alexa skill with my mobile application in AWS (Dev mode testing) | AWS re:Post