Symptoms

1. Device appears offline in Protection Console. 
2. When you check Acronis services on the machine, Acronis Agent Core service is stopped and fails to start (without any changes on machine, updates, etc)
3. Aakore logs contain errors similar to:

   C:\\ProgramData\\Acronis\\Agent\\var\\aakore\\host-alias.yaml': yaml: control characters are not allowed"}
   {"time":"2021-11-05T10:02:52+02:00","level":"error","msg":"creating http server: loading host alias table: file storage load 'C:\\ProgramData\\Acronis\\Agent\\var\\aakore\\host-alias.yaml': yaml: control characters are not allowed"

   The affected file may be host-alias.yaml or other file with .yaml extension

Cause

A  configuration file that is required for service to start got corrupted due to power loss or another environmental issue.

Solution

If a backup of the machine is available: recover the .yaml file from backup

OR

Delete the affected .yaml file and start Acronis Agent Core service again; the file will be re-created automatically.

More information

See also Acronis Cyber Protect Cloud: machine is offline in Cyber Protection console