Example of working JSON file for Dreambooth extension
JSON starts with { and ends with } and it shouldn't have a space before or after. You cannot include comments like you can with js.
Never leave a comma at the end, always use double quotes " not single ' and make sure it follows something like...
{ "objectProp1": "object content", "objectProp2": "object content with no comma because it's the last prop in the object" }
You can also have nested properties but the general rules above typically apply. This is from memory so might be a bit wonky but if this fails to help, use a online Json checker to see if your Json is valid.
If you have funky emojis and stuff maybe you will need to "escape" them, Google html encoding or Json character escaping to get the friendly versions of unicode characters
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