You will only see the Archived backups if the SnapMirror update command is triggered and is successful in the backup job (visible in the reports). Even if you see "Failed to update SnapMirror relationship" because another snapmirror update is in progress and the vault snapshots transfer fine you won't be able to see the Archived backups in the GUI.
Failed to update SnapMirror relationship.
Command execution stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Another SnapMirror operation is in progress.
vs
Initiating the SnapVault update on secondary...
SnapVault update initiated successfully on secondary.