The most possible cause is that Acronis Group Server cannot connect to the machine with Acronis True Image Agent to retrieve the status
Unmanaged
Remove the grayed out machines from Acronis Management Server and then add them back to solve the issue
This has been fixed
Acronis Storage Node does not support swapped drives. Managed vaults should only be created in permanent locations
How to create centralized vaults in Acronis Backup Advanced (Acronis Backup & Recovery)
To restore from an unmanaged vault, browse to the network share or local folder where the archive is. To restore from a centralized managed vault, click on Storage node, type in the IP Addres or computer name of the machine where Acronis Storage Node is
A vault is a location for storing backup archives
This article explains the general concept of archives and backups as realized in Acronis Backup & Recovery, and how one can resume previous backups into the same archive
Acronis Backup Advanced 11.7, Acronis Backup Advanced 11.5 (Acronis Backup & Recovery 11.5) and Acronis Backup & Recovery 11 centralized unmanaged vault metadata and locks differ from those of Acronis Backup & Recovery 10
The issue is fixed starting with the build number 37608.
How to upgrade tape vaults from Acronis Backup and Recovery 10 to Acronis Backup and Recovery 11