var jsonJSON = UrlFetchApp.fetch("https://wowtoken.info/snapshot.json");
var json = Utilities.jsonParse(jsonJSON.getContentText());
var max24 = json.NA.formatted.24max;
Instead of removing the numbers in front of the object names during parsing, you can also access the object's property like you would access an array element like so.
_. That is the reason why you are getting an error instead.