aws-s3-bucket-browser: Page shows but no listing and no errors in the console

I have a bucket with a sub folder, I’ve specified the bucketUrl as:

http://bucketname.s3.amazonaws.com/?prefix=subfolder/index.html

The S3 Bucket Browser page loads but nothing is listed. There are no errors in the console. If I go to:

https://bucketname.s3.amazonaws.com/?prefix=subfolder I do get a ListBucketResult with the contents shown.

I’ve tried other combinations but can’t get the page to load or I get no listing. Any suggestions?