question

Hi, I've been trying to test publishing a listing to the sandbox with ebay's Trading API Auth'n'Auth. I am using python ebaySDK, and hosting it on heroku. In the section "get a token from eBay via your application", I am clicking on "Auth'n'Auth", and then "test Sign-in", which takes me to a sign in page . I then sign in to one of my sandbox accounts, and click agree. Then it takes me to my app's return URL, which looks like this:

https://my_application.herokuapp.com/return_url/?ebaytkn=&tknexp=1970-01-01+00%3A00%3A00&username=testuser_example

In my program, I am then connecting to the API and making a GetSessionID call to eBay, which seems to work fine, and then making a call to Fetch Token with that session ID. I tried doing this two days ago and it worked fine, successfully publishing a test listing to the sanbox user's page. When I tried to do it again yesterday, it returned the error in the title:

ebaysdk.exception.ConnectionError: 'FetchToken: Class: RequestError, Severity: Error, Code: 21916017, The end user has not completed Auth & Auth sign in flow. The end user has not completed Auth & Auth sign in flow.'

I have not been able to fix this since and have no idea what's wrong.

My code:

from ebaysdk.trading import Connection
import requests
import xml.etree.ElementTree as ET


'''Establishing API conncetion'''

api = Connection(domain='api.sandbox.ebay.com', appid="app_id", devid = "dev_id",
                     certid = "SBX-cert_id", debug=True)


'''Making GetSessionID call to get session ID of the user who logged in'''

request = {
    'RuName': "my_ru_name"

}

sess_id_response = api.execute('GetSessionID', request)

# parsing response
root = ET.fromstring(sess_id_response.text)

sessionID = root[4].text

'''Exchanging user's SessionID for a token'''

data = {
    'SessionID': sessionID

}

api = Connection(domain='api.sandbox.ebay.com', appid="app_id", devid = "dev_id",
                     certid = "SBX-cert_id", debug=True)

token_response = api.execute('FetchToken', data)

# parsing response
root = ET.fromstring(token_response.text)

token = root[4].text
print(token)