Even On Journeyman

[danconnors]

There's no finding the Inca trasure if it's near Gran Granada. There's also no finding a lost relative if it's not near some landmark (west of Santiago just doesn't hack it). So I found only one relative, and no Inca treasures. Tough break.

[grundlewood]

Try saving the game then dividing the plunder and return to your career, this should cause a re-spawn of the cities, treasure etc. any maps will update and you may then find landmarks etc. are showing.

[tiberiansun371alexw]

This usually cleared those damn bugs on the CD version at least, the problem is dividing the plunder can end your game if you're too old.

[<0°C]

I'm late to the party, but:

Regarding Gran Granada (or Campeche): try looking around the Bay of Honduras. Just as you crash on the land, you will find a lake there (Lake Izabal, in fact, but the game does not name it - it is actually barely visible on the in-game map). Whatever you are looking for should be in close proximity to this lake.
https://i.imgur.com/jQCwcOo.png (look at the red X, where the current location of my ship is marked - that's the spot)
https://en.wikipedia.org/wiki/Lake_Izabal
It's a well-known bug/oversight by the devs. It may also get triggered when things spawn "south of Campeche". It's a long way.

Regarding "west of Santiago": Are you playing a campaign before 1660? If so, "west of Santiago" might be referring to the western coast of Jamaica (rather than Cuba), which before 1660 would not have any major cities - at that point, Port Royale still has to be founded. Settlements and pirate havens don't count as reference points for maps in the game (because they are randomly generated and they vary at each playthrough, making them non-historical), so the game finds the closest real-life city to Jamaica - which is Santiago - and gives you an ambiguous lead.

One good rule to follow is to check whether landmarks (temples, shacks, dead trees, geysers etc.) are solid or if you can pass through them - just walk into them to check. If you are unable to walk through those landmarks, they are the ones depicted on the map you are investigating.

Please let me know how it goes. :)

[Ranger]

You can save before you start searching and the spend "years" searching. Hopefully find it and the reload and you know where to go. Also sometimes you have to think outside the box, as in the map is basically wrong or confusing. I have had a game where one of the 9 pirates was in a bay it was impossible to get to attack his ship, so you do occasionally get glitches but actual impossibility is rare.