By chance, are you trying to run the downloadable version on Mac or phone? The downloadable (offline) version only runs on Windows, and there's sadly nothing I can do about it as I did not make the Quest 5 engine. I am hoping Quest Viva will be able to run on other systems when it is released, but nothing is confirmed yet. For now, you must use the online version instead: https://play.textadventures.co.uk/Play.aspx?id=cmt50dll2koybs5hqny8qa
If you are on Windows, you must download Quest itself onto your computer in order to run the downloadable (offline) version. This can be found in the download section of this game, or can be found on the official website here: https://textadventures.co.uk/quest/desktop