Appliance issues: Failed to mount the SMB share. 'SHARE-NAME'.

Suddenly we are having issues backing up through the vmprotect appliance, it seems there is authentication issues and its not clear why.

Here is a log from the failed backup.
Command 'Running backup plan 'Plone VM Backup - Full 1st Wed 12:00 Diffs every other day 1:00am'' has failed.
Additional info:
--------------------
Error code: 61
Module: 309
LineInfo: 4a8728dc8a1c950f
Fields: $module : mms_bundle_glx_pic_37687
Message: Command 'Running backup plan 'Plone VM Backup - Full 1st Wed 12:00 Diffs every other day 1:00am'' has failed.
--------------------
Error code: 41
Module: 307
LineInfo: e6792a5ee190dda7
Fields: $module : agent_protection_addon_glx_pic_37687
Message: ProtectCommand: Failed to execute the command.
--------------------
Error code: 32834
Module: 114
LineInfo: c35c04057128fda9
Fields: $module : disk_bundle_tape_off_glx_pic_37687
Message: Backup of virtual machines has failed.
--------------------
Error code: 32853
Module: 114
LineInfo: c35c04057128fdeb
Fields: $module : disk_bundle_tape_off_glx_pic_37687
Message: Not all virtual machines have been backed up.
--------------------
Error code: 32852
Module: 114
LineInfo: c35c04057128fe3d
Fields: $module : disk_bundle_tape_off_glx_pic_37687
Message: Failed to back up virtual machine 'PLONE'.
--------------------
Error code: 200
Module: 161
LineInfo: b320396adfe3b55
Fields: IsReturnCode : 1, $module : disk_bundle_tape_off_glx_pic_37687
Message: Failed to get archive URIs from location '\\nas\share-name\Plone\'.
--------------------
Error code: 200
Module: 161
LineInfo: a0f87a51d6f9cc76
Fields: IsReturnCode : 1, $module : disk_bundle_tape_off_glx_pic_37687
Message: Failed to get archive URIs from location '\\nas\share-name\Plone\'.
--------------------
Error code: 640
Module: 64
LineInfo: a1d3981537c68766
Fields: $module : disk_bundle_tape_off_glx_pic_37687
Message: Failed to open the metadata directory.
--------------------
Error code: 20
Module: 4
LineInfo: 72bd8f1a411be0dd
Fields: $module : disk_bundle_tape_off_glx_pic_37687
Message: Access to the file is denied.
--------------------
Error code: 80
Module: 89
LineInfo: 9d05ddc01e814e2f
Fields: $module : smb_supp_glx_pic_37687
Message: Failed to mount the SMB share. 'share-name'.
--------------------

We see why its failing after looking at the QNAPs connection logs, the appliance appears to mount an SMB share using just a username without the domain prefix. i.e Username VS domain\username

We have a Windows VM that is backed up using the same method and it has not had any problems ... yet.

Edit:

I just tried to do a restore of a file from the windows server and had the same problem, this is now a much more major problem.