Exactly same problem here. Worked fine for a few days, until today. Same error:
“There was an error attempting to check the permissions of the bucket xxxxxxx: Error executing “PutObject” on “https://xxxxxxxxxpermission-check.txt”; AWS HTTP error: Client error: PUT https://xxxxx/wp-content/uploads/2022/07/xxxxx-permission-check.txt resulted in a 403 Forbidden response:”
Ok, thanks! Just one more question about this: is there a way to filter only recent posts to preload? I have more than 30,000 posts, and preload the entire sitemap is not an option.