To found or conquer a new village you need a free expansion slot. To check whether your village still has an open slot you just need to go to your residence or palace and open the “Expansion” tab therein.
What does this mean for you?
In case you conqer a village, it can be that the old owner already founded one, two or three village(s) from it. Player abi (marked in red) conquered a village of player eblis.bm (marked in green) in the example shown below:
As you can see, there is already 1 expansion slot used by player eblis.bm.
If this happens to you, then you will only be able to found as many villages as you have open expansion slots. So if he found one villages already (as in the example shown above) then you cannot found or conquer one additional village with a residence level 20, and you can found or conquer two more villages with a palace level 20.