The ClientID doesn't appear for any of my clients, see screenshot:
What's wrong ? I'll be needed it to access the API...
Have you generated an overall API key under account settings? If you have and you're still not seeing the client API ID could you email in to support and let us know which client it is? We'll take a look.
Well, I give the answer to my own question: it appears that my API Key was quite old (there was a message indicating it was quite old but I didn't notice it...). There was a link for updating it. I did it and then the ClientID appears as expected.
Thanks for the help.