It is surely portugal anchorage, not by other nation ? AFAIK anchorages have no def garrisons so they shold be automaticaly captured.
You can try to add garrison to it in building model (you need to delete cache file- easier, but first load will be much slower or modify it - harder, but start is normal), and wait for it, to spawn garrision, overrun it, and captures shold be done.
Revert file back to original

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