Correct IAM settings for Amazon S3 bucket
You need to allow to list bucket location. Also, I'm not confident if you'd be able to upload and delete objects from the bucket with that policy.

I'd go with:

{
"Version": "2012-10-17",
"Statement": [
    {
        "Effect": "Allow",
        "Action": [
            "s3:ListAllMyBuckets"
        ],
        "Resource": "*"
    },
    {
        "Effect": "Allow",
        "Action": [
            "s3:GetBucketLocation",
            "s3:ListBucket",
            "s3:PutObject",
            "s3:GetObject",
            "s3:DeleteObject",
            "s3:GetObjectAcl",
            "s3:PutObjectAcl"
        ],
        "Resource": [
            "arn:aws:s3:::bucketname/*"
        ]
    },
    {
        "Effect": "Allow",
        "Action": [
            "s3:GetBucketLocation",
            "s3:ListBucket"
        ],
        "Resource": [
            "arn:aws:s3:::bucketname"
        ]
    }
]
}