Hi! I have the same problem. Settled all four islands, even won the game, but I didn't get the achievement. This is, I think, the THIRD time I managed to settle all four islands and still I didn't get the achievement. I didn't realize I would need a screenshot to prove it, so I don't have one.
@Administrator I saw the same issue just now. Was excited to get a city, but turns out, I can't cause I need ore instead! This was when I was playing my first seafarers game through Arrival on Catan. Thanks in advance for fixing it!