Error Message
A warning message regarding Download of disk descriptor file(vmdk) is logged during backup .

[Warning] From: VEPALIB_VMWARE@hostname "/Datacenter" Time: YYYY/MM/DD HH:MM:SS
[172:512] Virtual Machine 'New Virtual Machine': Download of disk descriptor file ('xxxx.vmdk') failed.

Cause
There is a potential risk that the VM was not backed up correctly, and the VM can not be restored .

According to debugs, the user was not allowed to download the vmdk file .

[ 20] [VepaHttpSession::getDownloadStream] =============================================================
[ 20] [VepaHttpSession::getDownloadStream] HTTP/1.1 401 Unauthorized

[ 20] [VepaHttpSession::getDownloadStream] =============================================================
[ 20] [VepaHttpSession::getDownloadStream] Error getting download stream /folder/xxx/xxxx.vmdk?dcPath=Datacenter&dsName=xxxx
[ 20] [VepaHttpSession::getDownloadStream] Throwing exception: class VepaHttpException

[ 99] <<=== (7) } /* VepaHttpSession::getDownloadStream */
[ 99]
[ 20] [HttpUtil::getFile] HTTP exception https://hostname:443/folder/xxxx/xxxx.vmdk?dcPath=xxx&dsName=xxxx
[ 20] [HttpUtil::getFile] UnLocking...
[ 20] [HttpUtil::getFile] UnLocking finished successfully.
[ 20] [HttpUtil::getFile] Error downloading filehttps://hostname:443/folder/xxxx/xxxx.vmdk?dcPath=xxx&dsName=xxxx
[ 20] [HttpUtil::getFile] Throwing exception: class VepaHttpException

[ 99] <<=== (6) } /* HttpUtil::getFile */
[ 99]
[ 20] [HttpUtil::downloadFile] Could not download File https://hostname:443/folder/xxxx/xxxx.vmdk?dcPath=xxx&dsName=xxxx
Download from https://hostname:443/folder/xxxx/xxxx.vmdk?dcPath=xxx&dsName=xxxx failed

The error indicates the user doesn't have the following privilege .

Datastore -> Low level file operations

Workaround / Fix
If the user actually has the privilege, there might be some unexpected issues regarding the privileges with the user .
Please consider to recreate the user with right privileges, or try to use another user that has the privileges .
Regarding the required privileges, please refer to a documentation .

Ref.) https://docs.microfocus.com/itom/Data_Protector:2020.08/VMwareConfigureIntegration