OK, OK, OK, thank you all for your kind cooperation. In fact I was using an Api Key which was not a Maps Api Key.
Everything is written in English, it's not always easy for me, who doesn't speak Shakespeare's language, to understand correctly.
Last question. So I created a Maps Api Key and now it works fine. It looks like I created this API Key for free and probably for a trial period. So I imagine it is only temporary. What is the procedure to be able to use it definitively. I could not find the section to convert it.
Thank you again and please excuse me for the inconvenience and for my poor English with Google Translate.