I followed the developer tutorial to set up the Google Indexing API tool in our Blogger workspace. I created a Google Cloud project, generated the Service Account JSON key file, and uploaded it to the tool.

The JSON key loaded properly and shows my Project ID in green. But whenever I paste my blog post URL and click Submit Request, after the 5-second countdown I get this error alert:

Permission denied by Google. 403 Forbidden

My account has enough coins, and the post is live on my blog. What step did I miss during the Google Cloud or Search Console setup? Would appreciate any step-by-step help!