Google Docs Spreadsheet to JSON

You may consider use an alternative to this request of your sheet data, because this method is deprecated. Anyway, you can still using another feed format, you can see this alternatives in: https://spreadsheets.google.com/feeds/worksheets/your-spreadsheet-id/private/full

In that result you can see any export formats are availables. Can help you an CSV or alt JSON visualization format?

The src attribute in your script tag is an invalid link (and you can see this for yourself by viewing your link directly in a browser).

The feed/key/worksheet section of the URL has the right key but the wrong feed and worksheet.

In the URL, replace "feed" with either "cells" (separate value for each cell) or "list" (separate value for each row).

At the same time, replace "worksheet" with "od6" (indicating the leftmost, or default, sheet - see this blog post for accessing other sheets).

If you view this new URL directly in a browser, you can see that it returns a meaningful value.

Your final script tag might look like this:

<script src="https://spreadsheets.google.com/feeds/list/1SKI5773_68HiSve1fsz7fr4gotjFWHB7KBuVsOlLz6I/od6/public/values?alt=json-in-script&callback=importGSS"></script>

For more info, you can see an example on the Google Developers site

APISpark PaaS has a feature to create and deploy a custom JSON API based on a GSpreadsheet. That might help and give you more control on the web API (CORS support, authentication, custom domain and so on).

See the tutorial here: https://apispark.com/docs/tutorials/google-spreadsheet