ERROR UPLOAD XML FILE - PYTEST - ZEPHYR SCALE

I am using pytest and have generated an xml file to import into zephyr.

Code that made me generate the xml file (I got this code from Smartbear - Configuring pytest to output JUnit XML results file): 

pytest --junitxml=output/junitxml_report.xml

I'm setting up the zephyr scale in jenkins. I start my work and get the following error:

Zephyr Scale] [INFO] Publishing test results...
[Zephyr Scale] [ERROR] There was an error while publishing test results to Zephyr Scale and they were not sent. Error details: 
Build step 'Zephyr Scale: Publish Test Results' changed build result to FAILURE
Build step 'Zephyr Scale: Publish Test Results' marked build as failure
Finished: FAILURE

 What is the problem?