Guide
Portuguese citizenship through a grandparent, and the connection test
Updated
The grandchild route is the one most people arrive looking for, and it is the one where the most money gets spent on the wrong half of the problem.
Two conditions, joined
The situation is listed as "Neto/a de avó/avô português originário e possuir laços de efetiva ligação à comunidade nacional". Grandchild of an original Portuguese grandparent, AND possessing ties of effective connection to the national community.
The conjunction is not decorative. Both halves have to hold, and they are established in completely different ways.
The genealogy half
The grandparent must have been Portuguese by origin. That is a status question about them, answered by their birth record, and it is not affected by emigration or by a later foreign naturalisation.
This half is documentary and finite: birth, marriage and death records establishing an unbroken line from the grandparent to you. It is work, and it has an end.
The connection half
Ties of effective connection to the national community is about the present. Family in Portugal you are actually in contact with. Use of the Portuguese language. Property. Time genuinely spent there. Continuing involvement in Portuguese life in any concrete form.
It is assessed on your facts, and how it is assessed in practice is not something a website can tell you: that is exactly the question to put to a consulate or a Portuguese lawyer at the start rather than at the end.
What can be said with confidence is the failure mode. Somebody with a genuine grandparent and no current connection responds to uncertainty by buying more certificates, which strengthens the half that was never in doubt.
Two better moves
Check whether your parent has a claim of their own. A parent in the transcription route carries no connection condition, and a transcribed parent moves you onto the parent route rather than this one. This is the highest-value question in the whole area and it is asked far too late.
And consider that connection can be built rather than argued. Language, time spent, family contact and property are things that can genuinely become true over a few years. On this route that changes the answer rather than dressing it up, which is unusual and worth knowing.