[2021] Fish Oil Factory ?? Can´t place it anywhere on coast after last update ??

Hey, so there are two possible causes:

One is a mod, that impacts your harbor area. So, if you're using any mods, please remove those and verify the game files. Or wait, till there's an update for the respective mod.
As usual, using mods of any kind happens at your own risk.

Secondly, you always need to leave some space so that all buildings have access to the ocean, you can't build "walls" all around them.
Feel free to share a screenshot of the issue, if you can rule out mods causing the problem.