Written with people moving from Turkey in mind. The Portuguese rules still apply more broadly.
Registering on the AIMA Portal
If the link on your visa sticker doesn't work, you must register manually on the AIMA/SEF portal. When asked for "Título de Residência", do not panic. Use your visa number, but often the system requires the "Body" number (top right) rather than the visa number itself.
If registration fails repeatedly, try different browser combinations or clear your cache. The system is notoriously glitchy with foreign IP addresses, so using a VPN set to Portugal might help.