What error are you recieving? What version of the API is in use? And do you have a sample of the code used?
Also, are you uploading changes to the data or to the actual views? I ask because it might be simplier to use tableau refreshextract with tabcmd or from the command line just calling 'tableau refreshextract --config-file'. This is how I refresh the views we utilize here in the Community for Ideas and Crow's Nest each day.
Tableau Data Extract Command-Line Utility covers this near the bottom of the page. This is particularly helpful if you have a pc to do the extract refresh that has access to the data source but your server does not.
Finally you can schedule the refresh of extracts directly on the Server if the server can access the datasource.
It turned out it was an encoding problem with the .twbx (zip) file. I changed the encoding before uploading the binary data to iso-8859-1 and it started working.
I am having this same problem of encoding .twbx file in the request body. Would you please provide the procedure you used to send .twbx file via request body. What should be the content of file (binary ? bytes ? String ?).