Hi Scott,
Yes, I did verified, our public ISP is Arsys, which the 4th largest in Europe and very well equipped. We have our own Virtual ISP based system there which is a LAMP and actualized.
In this moment I think my problem is with the type of account I have with PayPal, which I suspect does not support the Express Checkout I need for the cart.
This my first usage of PayPal services to receive payments, and I'm still learning. Also PayPal site does not guide us very well. Nevertheless, I will check that aspect this afertoon, and make myself sure that I have the right account with PayPal to access from the cart.
If you have recommendations on what I should have and / or check at payPal as account type, services and permissions to have and grant I will appreciate very much.
regards,
Vitor Dinis
Cibersur, Lda.

Hi Scott,
I have run the servertest.php on the production server at Arsys.pt - I added it here for you to check, but to me it seems ok.
Regards,
Vitor Dinis
Cibersur, Lda.

Hi Scott,
Good news, now it working.
Leave here my thanks to all and specially to you.
What were the problems ?
Wrongredentials !, that I got from PayPal - please all be attentive to go for a SIGNATURE and not a certificate..., then please be aware that you need to select as usage to your signature an EXPRESS CHECKOUT.
Then the remaining is straightforward.
Just for security I am now using still part of the menus in english, and I will translate them step by step, checking at each step if everything is working.
Regards,
Vitor Dinis
Cibersur, Lda.