Approving email template via API always fail

[Luis_Dalmolin]

Hi there, 

I'm working on a system that creates email templates and approves them via API. We had everything working fine, but last week we started receiving API errors when approving the template. The errors are not really helpful as they are always the 611 - System Error error message.

Here is the one example of a template that is failing: marketo-template.html · GitHub 

If I go to Marketo and manually approve the template, it works. Also, if I create a new template with this content and approve it, it also works. It only fails from the API.

Any ideas what could be happening? 

[Luis_Dalmolin · Accepted solution]

So it turns out the the only thing missing in my API request is to set the header to Content-Type: application/x-www-form-urlencoded.

Would help to get better error messages, but anyway, that's the solution.