I am using the Bubble API connector plugin to call a Postmark template and when I go to initialize the call in the Bubble terminal, I get this error, but I have no idea what it means or what to do about it. Help!
This is my cURL code:
So the body of your call at the moment contains the entire Curl command - this is not what is expected. You can see you are providing the endpoint (as you’ve got in the post url) plus the headers (as you’ve got in the headers section of the api call)
If you go back to the docs: Templates API | Postmark Developer Documentation and check out the ‘example body format’, or just take the body you have above (everything after the -d), you should have more success 
