"must" is being used here in a polite, figurative way.
In a strong upper-class British accent: "Oh! You simply must try the lamb, darling! It's devine!"
It means "should", but can't be translated as "should", because that is "devriez"; not "devez".
Devez can be should or must
Can "Vous devez goûter l'agneau", not be "you must try lamb", in a general sense?
should, in french seems correct too
The new female voice actually flubbed this one, I am surprised, it has been really great in every other example it has been used in that I have come across!