Unable to recognize the file type- error

I am trying send .jpg and .pdf files to api service, but always get this report. May be Content-type is invalid? I have tried different variants, but nothing heps. Would be glad to any predictions for solving the problem.

If you test the connection with Postman, do you get the same result?

You probably know it, but just in case: Postman is a free Chrome app, see Free OCR API

If you see the problem even with Postman, a screenshot of the result could be helpful.

With Postman I got normal result. What I have to change in my application code?