No, it just looks like there is a mismatch between what you’re loading and what you have specified.
As you’ve mentioned, the URL in the head has:
https://fonts.googleapis.com/css2?family=JetBrains+Mono&family=Playfair:wght@500&family=Roboto:ital,wght@0,400;1,900&display=swap
The important part being:
family=Playfair:wght@500
That particular element has a font-family of:
font-family: Playfair Display,serif;
There is no Playfair Display so it’s appearing as serif, but if you change it to Playfair,serif then you’ll see the font change.
Note that if you have Playfair Display installed on your computer locally, it would explain why you may see it there while others may not.