Magento – How to provide a valid OAuth/NLAuth authorization header for NetSuite

Being new to NetSuite and Post Man, I wanted to get my very first RESTlet up and working using Token Based Authentication which I have already set up, therefore I have:

• Account ID
• Application ID
• Consumer Key
• Consumer Secret
• Token ID
• Token Secret

This particular role designated already has Web Services only checkbox ticked as it was indicated in a few guides I followed. I also added permissions appropriate to their intended task.

I am currently experimenting tests through my Post Man REST Client by inserting my RESTlet's external URL into the address bar, included the following header keys and their values: (Using the format > Key: Value)

Content-Type: application/json
Authorization: OAuth realm="###",oauth_consumer_key="###",oauth_token="###",oauth_signature_method="HMAC-SHA256",oauth_timestamp="?????",oauth_nonce="?????",oauth_version="1.0",oauth_signature="?????"

I already replaced the hashes ### with my NetSuite provided information, however anything marked with question marks ??? are generated using php code . (Sensitive information were intentionally removed and left blank on here)

As a result, I received a 403 Forbidden error ("InvalidSignature" on our saved search Login Audit)

{
    "error": {
        "code": "INVALID_LOGIN_ATTEMPT",
        "message": "Invalid login attempt."
    }
}

As an alternative, I have used NLAuth approach instead to no success:

NLAuth nlauth_account=#####, nlauth_email=###@###.###, nlauth_signature=######

Where the hashes contain my account ID, related email address and the password respectively. I have also tried nlauth_otp containing my usual 6-digit pass code from my authentication application.

Regardless, I received a 401 Unauthorized error (< Blank > on our saved search Login Audit)

{
    "error": {
        "code": "TWO_FA_REQD",
        "message": "Two-Factor Authentication required"
    }
}

Since this is my first RESTlet, I was attempting to display product inventory from NetSuite to products stored on Magento.

In terms of researching done within Magento DevDocs, I have followed DevDocs and created an instance of an Integration API with the intent of being able to link more content to and from NetSuite and Magento in the future.

As a form of troubleshooting, I did try the Post Man's Authorization tab for OAuth 1.0 but I received a 400 Bad Request error after entering my TBA credentials in.

{
    "error": {
        "code": "INVALID_REQUEST",
        "message": "The request could not be understood by the server due to malformed syntax."
    }
}

I admit I am leaving something out unintentionally or have forgotten a step somewhere before here. Any help would much be appreciated.