Unable to login to MTurk using IAM user

The use case is indicative that you have a large number of assignments (a team of engineers would be using the service) and as such we can use the following guardrails:

1. The Amazon Mechanical Turk command line interface (CLI) makes it easy to use most of the Amazon Mechanical Turk functionality. When you wish to have a hands-on approach to using Amazon Mechanical Turk and have a relatively small number of assignments and results, the CLI is a good choice. For more information, go to Amazon Mechanical Turk Command Line Tool Reference.

2. When the number of assignments you have or the number of results you have is large, the Amazon Mechanical Turk API is a good choice. The API exercises all of Amazon Mechanical Turk's functionality and enables you to integrate Amazon Mechanical Turk functions programmatically. For more information, go to Amazon Mechanical Turk Developer Guide.

3. If you have a very large number of similar HITs, consider using the Requester user interface. It merges one question template with lots of question data to create many similar HITs. For more information, go to Amazon Mechanical Turk Requester User Interface.

You can refer to the following blog for a step-by-step on using the API:

Tutorial: A beginner’s guide to crowdsourcing ML training data with Python and MTurk

I was browsing the mturk website and checking the requirements for non-root user logins and I would like to pull your attention to step 3:

https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMechanicalTurkGettingStartedGuide/SetUp.html#create-iam-user-or-role

Step 3: Link Your AWS account to your MTurk Requester account Next, you will need to link your AWS Account to your MTurk Requester Account. This operation grants permission to your AWS Account to access your Requester account using the MTurk APIs. Go to https://requester.mturk.com/developer. Click Link your AWS Account and sign-in with your AWS Root user email address and password.

Can you please audit your steps and see if this works?

As you can see from the documentation - this operation grants permission to your AWS Account to access your Requester account using the MTurk APIs. And you have an exhaustive list of activities that you can perform using the APIs as can be seen here: https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/Welcome.html

However, if the question is how else can you access the Mechanical Turk, then the answer is: You can access Amazon Mechanical Turk (Mechanical Turk) using the Mechanical Turk requester user interface, the AWS Command Line Interface (AWS CLI), or the Mechanical Turk API. https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMechanicalTurkRequester/AccessMturk.html

Does that answer your question?