The specified user cannot be found

Hi

I am new to OneSpan and trying to going through following blog  

https://www.onespan.com/blog/onespan-sign-how-making-rest-calls-onespan-signs-api-python

But i am getting following response 

{"code":404,"messageKey":"error.notFound.userNotFound","technical":"Could not find user with uid 'Mrx4UBnpkHc4'","message":"The specified user cannot be found.","name":"Resource Not Found"}

However when i use interactive API tool at following link 

https://community.onespan.com/products/onespan-sign/sandbox?origin=docsesignlive#/

and submit the following request 

curl -X POST "https://sandbox.esignlive.com/api/packages" -H "accept: application/json" -H "Authorization: Basic my_api_key" -H "Content-Type: application/json" -d {"name":"YourTransaction"}

I am able to receive a response 

{ "id": "aBQT0cuFKsGjK2j6_LSUYZRmpA0=" }