Thank you very much Kano and Bitmax for your kind replies. Have 2 new babies in the house and I don't have access to pc often these days. Here are my replies to each of your questions and feebacks.
To Kano: I studied the api-readme, I have the commands enabled in my api group. As a matter of fact when I issue the command via SSH I do not get forbidden reply from the api, I receive the missing pool ID reply. I do not use W: group as I had some issues in understanding what IP where my commands being received from, so I changed the default api group adding the commands I needed and it seems to be working fine. I know you wrote the api and the readme, so I'm really super-happy you are actually replying to me in person!
To Bitmaxz: I am working on several machine types (bitmain Antminer L3+, t17, s17, if I can make the few changes I need I would really need also to extend the work to s19). I send the commands via ssh interface.
Thank you so much for your help!
Francesco