Why is my FORMAT function not working?

[Nietzsche]

Hello,  I am doing an Udemy course on Power BI

In the instruction video, the instruction put in a formula like this

Month Name = FORMAT([SalesDate], "MMMM")

And he got column with Month spelt out like this

But when I do the exact same thing, I am still getting date in the dd/mm/yyyy format.

Why is this the case?

[Nietzsche · Accepted solution]

Had to convert SalesDate column to Date format in Power Query Editor first, now it is working.