After many and many time of research, I have found the problem.
The proxy system was strangely configured (with a list of proxy URLs in HTTP and HTTPS).
I deleted this list and replaced by only one proxy URL.
I also replace “Get File” keyword by “Load JSON From File” to be sure that the file is in JSON format.
And it works.
Besides, I don’t know why…
I have done 2 tests :
One without proxy configured
Create Session mysession ${base_url} headers=${header} => It works
One with proxy configured
${proxyDict}= Create Dictionary http=My_proxy_URL:port https=My_proxy_URL:port
And my proxy system is configured with http://My_proxy_URL:port
Thanks at all for your time !