Problem solved!

Without doing anything (don´t know if application was updated), just opened LinkedUp and was directed to the right web address to authorise. Somehow, now the token number appears at the end of the address, which it didn't before. And I obtained the PIN successfully

Now it´s working perfectly and the application looks great!

I don´t have the community SSU or any other modifications. The only application installed that tweaks a bit the 'system' is Swappolube, but I doubt any conflict between the two. No idea why it happened. I´m in Spain.

Thanks for your help and the great work!