curl or url error: Invalid value passed for authtoken

curl or url error: Invalid value passed for authtoken

Hi, well, I'm preety new in Zoho, reading the api documentation and testing for a custom invoice implementation.

I'm stuck getting this error 
{"code":14,"message":"Invalid value passed for authtoken."} 

 Could not resolve host: 9688aa8....(hidden) 
Using: curl https://books.zoho.com/api/v3/organizations -H 'Authorization: Zoho-authtoken 9688aa....  in a windows environment (other api calls work fine)

The authtoken is valid, is created a few moments ago and listed in  https://accounts.zoho.com/u/h#sessions/userauthtoken

Am I missing something?

Thanks.

Marcelo Kaos