Hi
It's not the version of VP as it will pick up the fonts you have on your PC. Is it possible your version of Windows 8.1 hasn't got it installed? (My wife's Windows 8.1 here does not have Vivaldi......I use an old(er) Vista PC and it is there......?)

Do a search in your Table of Characters or better your Font folder. (In 8.1 search font not vivaldi) If you can't find it then you will need to download it from the web here and drop it into your Font folder.
https://www.wfonts.com/font/vivaldi
This might be the same link as Borate supplied
Nat