[BTS] Can't build A-bomb - grayed out option

[jimmywfl]

I have uranium, chain reactor, A bomb tech, can see the build A-bomb icon, but it is grayed out in all cities. I did cannot build the Manhattan since another player has built it.
What is my problem?

 

[Louis the XIV]

Is the UN Built? Because if yes then maybe there was a vote to ban nuclear weapons.

 

[Nogbadthebad]

Assuming the uranium is connected then you are probably just missing rocketry tech.