Error 50079 : Jmeter does not write file path.
According to your exception, jmeter cannot find the file to download due to the problem mentioned above.
Thus, you must set the path manually in the sampler, and it is better to use a variable for this, for test parameterization.
Do not use recording and playback at all, or at least check and tune recorded samplers. In your case, you need to set the following in the http [POST] request:
Use multipart/form-data for POST = true - send the file as part of the request;Send Files with Request -> File Path = PATH_TO_FILE - , .
. . .
UPLOAD HTTP Request
Method = POST
Use multipart/form-data for POST = true
-- Send Files with Request -- section:
File Path = ${testFile}
Parameter Name = datafile
MIME Type = ...
. . .