Banks

A bank gives -10 upkeep to units produced in the city with the bank. They do not need to be in the city. If you make a bank in london, all units produced in london have -10 upkeep as long as the bank stands.
And no they are not effected the same round, the bank's upkeep comes the following reinforcements round

I do some test and I see that the bank do not work

Did not understand, can a detailed explanation of the bank's operation?