Looking at some other posts this is what I have found:
- We need to create 2 httpRequests in this case, one for authentication and second for actual API request
- In the first call you send a POST request to
...../oauth/tokenURL with Form request body with these 3 fields
grant_type: client_credentials
client_id: __________________
client_secret:_______________ - Then use the
access_tokenin the body of the response from above in the header of next httpRequest
Authorization : Bearer {{$.hTTPRequest.body.access_token}} - Leave Authentication empty for both httpRequests
Here is the link where I found this
Also make sure you are using the right id field from Campaign Activated in the URL. There are 2 ids and it might be confusing when you pick the variable from inside Define Variable
Right one

Wrong one

And here is the test result
