Is everyone here playing on Android? I have the same problem. I've been playing and looking into the problem for months and so far couldn't get a solution.
On my end, I have several achievements, but I can't get any new achievements at all for months now. I don't know if that is the problem, but it sure as hell would prevent anyone from unlocking leaders, since they all require some specific achievement.
For example, look at me trying to get achievements Arms Dealer and Purchasing Secret on
this video if you will (I recorded it for the tech support guys). Nothing happens.
Then I recorded myself
following their tips (clearing data and cache) and winning a cultural victory with the french having built the Tour Eiffel. Nothing happens, achievement not registered and Charles de Gaulle is not unlocked.
I am back and forth with the tech support of 2K, they did reply but so far only gave me those obvious troubleshooting tips (restart phone, clear cache, clear data, reinstall game). None of that did anything.
Unfortunately it's a game full of bugs which last update was over a year ago. The devs clearly abandoned it. You should all contact support so perhaps they'll acknowledge the flaws and try to fix them.