PERMISSION_DENIED when testing PayPal Activity REST API in the sandbox

Question

I created a new app and I'm following the API instructions as documented here: https://developer.paypal.com/docs/api/activities/

My sandbox credentials are good, and I used them to create a bearer token, which I used (in Postman) to post a payment (https://api.sandbox.paypal.com/v1/payments/payment) with success.

However, my goal for this application is to create an activity report using the API functions linked above. For this, I turned on the appropriate "App feature option" called Transaction Search, in addition to every other app feature option.

Header:

Authorization: Bearer (new bearer token here)

My GET request:

https://api.sandbox.paypal.com/v1/activities/activities?start_time=2018-05-03T15:00:00.000Z&end_time=2018-05-02T15:30:00.000Z&page_size=10&next_page_token=1

Whatever I do, I get:

HTTP Status: 401 Unauthorized

Request body:

{
    "name": "PERMISSION_DENIED",
    "message": "No permission for the requested operation",
    "details": {
        "": "No permission for the requested operation"
    }
}

I am a US developer, and this application is for my own use.

Answer 1

Final answer (for now), confirmed by a PayPal developer support technician:

PayPal doesn't yet have a REST API method available to the public, for creating this report. Use TransactionSearch in the old NVP (Name-Value-Pair) API, it's reasonably well documented and used everywhere - even though it's been deprecated since 2017.

https://developer.paypal.com/docs/classic/api/merchant/TransactionSearch_API_Operation_NVP/?mark=TransactionSearch

For those who like to work with example code, the following GitHub project shows how you could implement the API. It was helpful to me:

https://github.com/gtaylor/paypal-python