The script works at your site.
http://www.meteotorrelavega.com/pwsWD/w34_WDapi.php?test&d=1
Returns correctly the error message.
Your screenshot shows more like a “page not found” type error.
Check the spelling as we can not see what is in the URL box, should be w34_WDapi.php without any spaces after it.
It does not upload yet as the data on your site is still the original download test-data
http://www.meteotorrelavega.com/pwsWD/w34_module_test.php => click on “Show WDapi values”
or use http://www.meteotorrelavega.com/pwsWD/jsondata/WDapi.txt
Wim