"TypeError: Failed to fetch" for valid response

I have imported the api and the swagger to the catalogue (after changing the target url and org_id).
I tested /getSteinwegHierarchyComboList and it looks like it’s working.
Can you specify what exactly are you sending?
Thanks,
Yaara

curl -X GET “https://letzit2.cloud.tyk.io/SteinwegHierarchy/getSteinwegHierarchyComboList” -H “accept: application/json” -H “Authorization: 59d27324b8125f000137663e4f159109e21046ca7c018c996ccc8224”

Response body:

{
“origin”: “151.228.199.234, 172.30.2.182, 172.30.2.111, 54.175.77.57”
}

Response headers:

access-control-allow-credentials: true access-control-allow-origin: https://letzit2.cloud.tyk.io, https://letzit2.cloud.tyk.io access-control-expose-headers: * content-type: application/json date: Fri, 10 Nov 2017 17:57:31 GMT server: meinheld/0.6.1 vary: Origin via: 1.1 vegur x-powered-by: Flask x-processed-time: 0.000478982925415 x-ratelimit-limit: 20 x-ratelimit-remaining: 16 x-ratelimit-reset: 1510340202 content-length: 76 connection: keep-alive