The ArchiveManagerAttachment Share is not available.
This can be caused by several environmental issues.
1. The share does not exist
2. The share is not accessible
3. The share is on a clustered server and is not a clustered folder
Ensure that the Data folder for Archive Manager is shared properly (Share Permissions - Everyone Full Control NTFS Permissions - Administrators and ArchiveManagerServiceUsers - Full Control)
Make sure that you can hit the share with these permissions.
If this is a clustered server, make sure that the folder is also clustered because if you cannot see it in Cluster Administrator, in a failover situation, the share will become unavailable.