There is no single answer to this question since the cause of a JSON format error can vary, but there are some general tips that may help you fix the issue.
Firstly, make sure that you have valid JSON. You can use an online JSON linter or parser to check your JSON for any errors. If your JSON is invalid, it will not be able to be parsed by JavaScript.
Secondly, if you are loading JSON data from a URL, make sure that the URL is returning the correct data type. JSON data should be returned with a Content-Type header of application/json.
If you are still having trouble, there are many other resources available online that can help you debug JSON errors in JavaScript. Try searching for a specific error message that you are getting, or for general tips on debugging JavaScript.