Bucket listing of a cloud provider fails when adding a bucket in the Cloud objects tab
Explanation
The most common reason for failure in bucket listing is when cloud credentials provided to NetBackup do not have permission to list buckets.
Another reason is when the cloud provider does not support proper DNS entries for endpoints. Similarly, a wrongly configured DNS or even a virtual-hosted style naming implies that no request can be issued to the cloud provider without providing a bucket name as the host name. An example of such a cloud endpoint is: s3-fips.us-east-1.amazonaws.com
Workaround
Although the bucket list is not available, you can always manually add buckets in the Cloud objects tab for backup.
When it is a DNS issue, you can optionally list buckets using a temporary workaround by adding an IP hostname-mapping entry in the /etc/hosts file. When only virtual-hosted style requests are supported, first prefix the endpoint using a random bucket name, when using commands like ping, dig, and nslookup to determine the IP of the cloud endpoint. For example,
ping randombucketname.s3-fips.us-east-1.amazonaws.com
You can then add the resulting IP along with the actual endpoint name (without the random bucket name prefix) in the /etc/hosts file.
Note that this is a temporary workaround to edit DNS entries on the computer for bucket listing. Remove them after the policy configuration is done, unless the cloud endpoint is a private cloud setup that can use static IP addresses permanently.