Troubles with settling a font family for main header

Hello, on this page, I am told to “In style.css, specify Playfair Display as the font family for the main heading, followed by serif as the fallback font.”
So, I wrote :
h1 {
font-family: Playfair Display, serif;
I run my test but I am told : Did you change the h1 font-family value to “Playfair Display”, serif?
What am I doing wrong ?

Thanks in advance for your help !

Just forgot the quotes " " since this is font with two words and a space ><