Need Help with Masteries (Possible Bug)

So I’ve decided to focus my first few games on the Delhi Sultanate and have been achieve the first mastery, which is to increase the yield of 6 berry bushes. This is accomplished by building a mill next to said bushes, however it does not seem to work, as I’ve yet to get the mastery. Do I have to win said game or do something else to get the mastery to register or is it just a bug.

I got it no issues. Did you build the mill before reaching Age II? It is a requirement for the mastery.