A user experiences the following symptoms in a hybrid deployment of on-premises Microsoft Exchange Server and Microsoft Exchange Online in Office 365:
When the user tries to access a cloud-based archive mailbox by using Outlook Web App, the user receives the following error message:
Your archive appears to be unavailable. Try to access it again in 10 seconds. If you see this error again, contact your Help Desk.
When the user tries to access the cloud-based archive mailbox by using Microsoft Outlook, the archive mailbox may be present in his or her profile. However, the user can't update the archive mailbox.
This issue may occur if the root certificates on the Exchange hybrid server are missing or corrupted. These certificates are used to validate your on-premises Exchange environment.
To resolve this issue, update the root certificates, and then rerun the Hybrid Configuration Wizard on the hybrid server. To do this, follow these steps. Be aware that these steps must be completed by an Office 365 administrator. If you are a user who is experiencing this issue, contact your administrator to resolve this issue.
Step 1: Update the root certificates
To update the root certificates, run Windows Update on the Exchange hybrid server.
For more information about how to update root certificates for a particular version of Windows or about how to use Group Policy to distribute updates, see the following Microsoft Knowledge Base article: