Failing conversion rule creation

Hello.

I've been recently trying to create a conversion rule through the Taboola Backstage API, as specified in the appropriate section of the documentation (https://developers.taboola.com/backstage-api/reference#create-a-conversion-rule).

In order to create the rule, I've been issuing a POST request to the following endpoint,

https://backstage.taboola.com/backstage/api/1.0/{my_account_id}/universal_pixel/conversion_rule/

with a correctly generated Access Token (I've been using it to call several other API endpoints as well and it worked in those circumstances).

My JSON body is:

{
"event_name": "test_pixel",
"display_name": "test_pixel",
"include_in_total_conversions": false,
"category": "SEARCH",
"status": "ACTIVE",
"type": "EVENT_BASED",
"condition": [],
"exclude_from_campaigns": false,
"look_back_window": 30
}

Even though there seems to be no inconsistency with the documentation (all fields seems to be correctly configured and no required field is missing, apparently), the API responds with an error:

{
"http_status": 400,
"message": "Bad request",
"message_code": "api.action.bad_request.null"
}

No meaningful message is associated with the response and I don't know how to make this work.

Thanks in advance for your support.