After SessionID was used to construct the SignIn URL, and after the eBay User authorized my application, When I tried to call FetchToken with a valid authorized SessionID, I see the error - "The end user has not completed Auth & Auth sign in flow". Why?
The error message you are receiving normally occurs if the authorisation process for obtaining your token was interrupted or not completed in some manner.
Please try either of these to fix the above error.
* Please check your SignIn URL for proper encoding. Please donot encode "&" between the GET params. for example
https://signin.ebay.com/ws/eBayISAPI.dll?SignIn&runame=TestRUName&SessID=XXXXXXXXXXXXXXXXXXXXXXXXX - This is wrong, this might malformat the GET params(SessionID).
Please change this to https://signin.ebay.com/ws/eBayISAPI.dll?SignIn&runame=TestRUName&SessID=XXXXXXXXXXXXXXXXXXXXXXXXX - This is correct.
* Once you have clicked on the required link you will be taken to eBay where you can log in. eBay should then present you with a 'Grant application access' page. Clicking on the 'I agree' button will generate your new token.When performing the process you should ensure that you do not navigate away from any page sent from eBay and if at all possible do not open multiple browser tabs when clicking on links.