It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

Moimoije: hello , check if you have unamployed MEN (not women :)
Alexandre31200: Tried it, doesn't work :/
From what I know, monastery needs a dorm and available unemployed men to concede a villager to the Monastery. Have you met those requirements?
Also, make sure to have a door attached to your dorm :)