Error when trying to connect API through Application Authentication Endpoint

I successfully created a REST API key and secret manually, which I could use in Postman to create and receive orders etc. However I’m unable to do the same when I follow the guide to generating API keys using the Application Authentication Endpoint. I’m receiving this error when I try and approve connecting a store to the API:

Error: An error occurred in the request and at the time were unable to send the consumer data.

I’m not super technical, my task is to create the documentation to pass onto the developers. This was a newly created store, set up just for testing. There are no products, no plug-ins (except for Woo Commerce), and it is up-to-date. I can’t find an option in the sidebar of my screen to get the system status otherwise I would attach that

We are trying to integrate our WMS and ERP system with WooCommerce, and my understanding is that we should direct our customers to a link like below, and when they approve it will create a Consumer Key and Secret that we can then use to connect to the API:

https://woo-mortally-noisy-theorist5.wpcomstaging.com/wc-auth/v1/authorize/?app_name=New%20Test%20App&user_id=12345&return_url=https://oauth.pstmn.io/v1/callback&scope=read_write&callback_url=https://oauth.pstmn.io/v1/callback

When I click on Deny, I get redirected to the callback URL with parameter success=0 as expected:

oauth.pstmn.io/v1/callback?success=0&user_id=12345

But when I click on Approve, I am directed to the URL below with the error underneath:

https://woo-mortally-noisy-theorist5.wpcomstaging.com/wc-auth/v1/access_granted/?app_name=New+Test+App&user_id=12345&return_url=https%3A%2F%2Foauth.pstmn.io%2Fv1%2Fcallback&callback_url=https%3A%2F%2Foauth.pstmn.io%2Fv1%2Fcallback&scope=read_write&wc_auth_nonce=0acaf32bf4

Error: An error occurred in the request and at the time were unable to send the consumer data.

Can someone explain what I’m doing wrong?

Thanks!

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