It costs money, but it is always better to get a portuguese speaking local tech to check out initial sapo installations and that your pc is configured properly.
PT engineers are only trained to install lines and equipment...not to make sure computers are correctly connected to the router or diagnose computer problems.
The call center folk at the SAPO help centre run through standard computer generated fault check lists and do not have the flexibility to diagnose problems specific router/computer installations.
I have come across this many times here. I have been called to clients have been sold SAPO accounts/routers. Installation is supposed to be self-explanatory. However, they try to install it and often find they can't or there is a problem. They get onto to the SAPO helpline and more often than not end up in similiar posiitons to those refer to in this thread. The latest incident occured last week, and althogh the client had some computer knowledge and had spent 3 hours on the phone to Sapo, as well having had a PT tech come to check the line, it took a visit from me and 45 minutes slog to find out that a single misplaced number in a not-obvious page of the control panel of the router, was the origin of the problem. Since then no hassle but SAPO were worse than useless.
It is not only estrangeiros who have this problem. I know of many Portuguese folk who have had the same frustrations.