When you generate an S3 credentials for Mountain Duck, you must use exactly the same encryption phrase used during upload, otherwise your objects cannot be decrypted and buckets will look like empty.
When I make a bucket, I have to generate a passphrase. Then, when I create S3 credentials, I have to generate a pass phrase.
When I set up Mountain Duck, I use the S3 credentials. If I want to access that information on web, when I open the bucket, I should utilize the pass phrase from the S3 Credentials, correct? If I use the bucket pass phrase, then the information would be hidden.
The encryption phrase is not tied with the bucket, it used to encrypt/decrypt your objects (in any bucket). So, you may generate an encryption phrase or use your own or use a previous one.
Even more - you may use an own encryption phrase for every single object, just to see objects you need to use the same encryption phrase used during upload of your objects.
So, to see objects in any tool you always should use the encryption phrase used during upload of your objects, and you will see only objects decryptable with this encryption phrase.