The tax law amended 6 June 2022, now only requires the appointment of a tax representative domiciled in Portugal when it is necessary to assist in the fulfilment of tax obligations by taxpayers residing in a third country (domestic and foreign not in the EU) and ensure the necessary contact between the Portugal tax authorities and the taxpayer.
Having a fiscal representative resident in Portugal is obligatory when the person is the owner of a vehicle and/or a property on Portuguese territory, or when the person works on Portuguese territory (whether for a third party, or as self-employed). The obligation for local fiscal representation is optional if the person resides in the EU/EEA.
Exemption from the obligation to have a locally resident tax representative occurs when the person is (i) not a tax resident in Portugal or EU or EEA; (ii) does not fulfil any legal requirements of having a Portugal tax status; (iii) is not subject to taxes in Portugal; (iv) has no tax obligations nor intends to have any tax obligations in Portugal. Information from the source (Portuguese Fiscal Authority- Autoridade Tributária e Aduaneira) is at: https://www.apeca.pt/docs/informacaoapeca/oc_90054_2022.pdf
I have seen statements that the obligation for local fiscal representative only exists during the period in which the person continues to own the vehicle/property and/or works in Portugal. After sale and/or ceasing to work in Portugal and fulfilling all tax obligations, the obligation for local fiscal representation ceases. https://eco.sapo.pt/2022/06/08/nomeacao-de-representante-fiscal-deixa-de-ser-obrigatoria-para-quem-nao-tem-obrigacoes-fiscais-em-portugal/. This makes sense, but I have been unable to find the source of this information.
So the answer for you depends on whether you have (or have acquired) tax obligations in Portugal, or not. If yes, the Portuguese fisc need to be able to be in touch with you through your local representative.