Look into both your portal - 6367222 and 4774178, while I'm able to see that both portal are on HubSpot free, they both have the free marketing email add ons (temporary). This means that using that portal you can send out marketing email temporarily. In this case, I would expect the endpoint to work.
On my end, when using this endpoint: Get all marketing emails statistics to get the marketing statistics for both your portal - 6367222 and 4774178, I'm able to see the return results just fine.
As I wasn't able to reproduce this and to ensure that our testing is consistent, would you mind trying it out again on an API client such as Postman?
Thank you for your response. I trust you are doing well 🙂
I've tried pasting the API call into my browser (it should work that way) and I'm getting the below result:
{"correlationId":"7d69becb-353c-4d4a-865a-5af9880527ac","message":"This hapikey (mykey) does not have proper permissions! (requires any of [content-core-api-access])","requestId":"4ac348ce-e06b-4af9-a990-83ec1367d468","status":"error"}
I don't think that this has something to do with PowerBI.