One of the reasons I found is the incorrect bucket naming convention. EV currently checks the bucket naming convention as per amazon recommendations and don't allow any other character in the bucket name for any region. To support that, please see the following link:
http://docs.aws.amazon.com/AmazonS3/latest/dev/BucketRestrictions.html#bucketnamingrules
"While currently, the US East (N. Virginia) region currently allows non-compliant DNS
bucket naming, we are moving to the same DNS-compliant bucket naming convention for the US East (N. Virginia) region in the coming months."
Also see the following comments in the link:
- The US East (N. Virginia) region currently allows more relaxed standards for bucket naming, which can result in a bucket name that is not DNS-compliant.
- To avoid this problem, amazon recommends as a best practice that you always use DNS-compliant bucket names regardless of the region in which you create the bucket.
- If you use the AWS management console, bucket names must be DNS-compliant in all regions.
So I suggest, you have bucket name as per Amazon recommendation character and check if the issue still persist.