5e Legacy Sheet Problem

So I was trying to use  this sheet  as a base to make a custom sheet for a Scrivened game my group is playing, and before I even made any changes, putting the html and css into the custom sheet field and loading the game gets me this: Anyone able to tell me what's wrong? The screenshot is after I renamed a few skills and such, but it does the same thing unedited, I checked.

You need to include the translation json file. There are three tabs you need to fill to install a custom sheet. The json file replaces all those red placeholders with wording of the appropriate chosen language.

I was using a json, but I was using the "sheet" json instead of the "_translation" json. Not exactly clear which one is for what at first.

I've never installed that sheet manually. Not sure why there are two JSONs, or what to do with the sheet.json.