We have no "Senate" in Pirates, but this sounds like "Captain's Quarters".

You don't have to upgrade any building, but a very specific one, most likely Manufactory (the one where you combine gold and lumber into gears).

To see what you need, simply click on "Upgrade":

i

The game will than show you what you're missing:

i

Even if you're not playing "Pirates", it should be the same in other Plarium games.

oh so it need to be maxed out ok thx