Although the emergency state has been extended until the end of April, SEF has issued a note in regards to the appointments:

“Citizens who have an appointment from April 19th will be able to do so. All others who have seen their appointments canceled, due to the suspension of public services, during the last few months, will receive an email from SEF indicating the new date.”
https://imigrante.sef.pt/en/covid-19/

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We will be on top of this subject and provide feedback in the coming weeks for future developments.