No error message is displayed on the Veritas Alta Archiving Administration console's Office 365's Job List section, however the below error can be seen in Azure AD Sign-In activity for the service account being used.
Access has been blocked by Conditional Access policies. The access policy does not allow token issuance.


An Azure AD Conditional Access policy is preventing service account's access to the Azure Active Directory PowerShell.
Review the Conditional Access policies of the tenant and create proper exceptions/exclusions for the service account to access the applications Azure Active Directory PowerShell & Office 365 Exchange Online(Exchange Online PowerShell) in Office 365.
Please refer to the article in Related articles for IP address information for O365 sync.