@niki_wiles There’s nothing obviously wrong with you request in terms of usage. Additionally, I’m able to successfully execute this request with twurl (see below):
twurl -H ads-api.twitter.com "/0/stats/accounts/18ce53ur22q/reach/campaigns?start_time=2016-01-06T00:00:00Z&end_time=2016-01-06T23:59:59Z&campaign_ids=3x9tp"
{
"errors": [
{
"code": "FEATURE_NOT_AVAILABLE",
"message": "The account does not have the feature REACH_AND_FREQUENCY_ANALYTICS",
"parameter": ""
}
],
"request": {
"params": {
"campaign_ids": [
"3x9tp"
],
"start_time": "2016-01-06T00:00:00Z",
"end_time": "2016-01-06T23:59:59Z",
"account_id": "18ce53ur22q"
}
}
}
Note that the response shows a different error because this account doesn’t have access to this white-listed feature yet, but the request is successful (eg. not a malformed request as your seeing). The fact that this works in twurl but not in your implementation would seem to indicate that the issue is not an API issue or a usage issue but something in your current implementation.
We’re limited on how much we can troubleshoot within your own implementation, but can you share more technical details about how you’ve implemented making this request?