Siege of Kazan Maximum Population Capacity

During the Siege of Kazan, I am unable to produce any more troops, villagers, etc. than what I’m given at the beginning. After I’ve built enough houses to support my population, plus more to support the army I want to build, I am unable to produce any population at all. Even after the enemy troops kill off the ones I start with, I am given the red warning message on all my production buildings that I cannot produce any people because I have reached my maximum population capacity. I can’t even build any siege vehicles. I can’t produce villagers to replace the ones that fall to enemy raids. Is there something I’m missing? I would appreciate any help! Thank you!