Hi Adriana, welcome to Upwork!
Please feel free to repost your comment in English on the same thread, so other users could respond and share their advice.
If she was writing that her Portuguese tax number is not being accepted by the Upwork system, then I am having the same problem.
I can verify my tax number on international tax websites, but for some reason Upwork is not accepting it. I tried putting "PT" in front of the 9 digits and also without it.
That site (vies), says my "VAT" number is invalid, but it's valid in Portugal! So maybe one of two things: (a) The tax number that Portugal issues is not compatible with the rest of the EU or (b) I need to be a proper company and not just be an individual which doesn't make sense at all! So if I can't provide a valid "VAT" number, I will be charged VAT... I will be charged VAT just for having an account on upwork with no work yet? That doesn't make sense!