When contacting Acronis Customer Central with a technical issue, it is recommended to have Acronis System Information at hand

Backup fails with:

The backup has failed because 'VSS Writer' has timed out during snapshot creation



Windows error: (0x800423F2) VSS writer 'System Writer' with class ID 'E8132975-6F93-4464-A53E-1050253AE220' has timed out. This may be caused by too intensive I/O on the machine at the backup start time. Try to re-schedule the backup to some different time. To troubleshoot VSS issues, download and run Acronis VSS Doctor available at https://www.acronis.com/en-us/personal/vss-diagnostic-free-tool/

This article is for Acronis Cyber Backup 12.5, Acronis Cyber Protect 15 and Acronis Cyber Cloud. If you are using Acronis True Image see this article instead.


Backup to Acronis Cloud fails with message:

Network connection failed due to timeout.


Backup fails with: 

Windows error: (0x8007001F) A device attached to the system is not functioning


Backup fails with: 

"Windows error: (0x8007045D) The request could not be performed because of an I/O device error"


Backup of a Windows machine fails with error:
Logon failure: unknown user name or bad password.


Acronis Cyber Backup agent receives this error from Windows while trying to access backup source or target.

This article describes how to use Web Restore to retrieve files or folders without using Acronis software.

You restore a machine to dissimilar hardware and apply Acronis Universal Restore.

The process completes successfully, but the restored machine goes to BSoD with error "Stop 0x0000007B".


You get errors when you use Acronis software to connect to  a mailbox or public folder via the Exchange Web Services (EWS) protocol.


To verify if an error is related to Acronis software or to the environment, you can use a tool called EWSEditor to connect to the mailbox or public folder that causes errors and check if the error appears. This can be very useful in scenarios when:


You try to add a shared folder or NAS as a backup location or want to recover files from this location.

When specifying credentials for remote resource, you get the following error
External IDs conflict for >1 credentials objects


Issue in the product.


Acronis Cyber Cloud: the issue is fixed in Agent build 26077.

Acronis Cyber Protect 15: the issue is fixed in Build 26172.

You want to register a machine with Acronis Agent in the management server. Registration fails. You check Acronis Managed Machine service and notice that it is stopped.

When you try to start the service, you get this error (logged in Windows event logs):
Error 0xb9000b: Failed to initialize network module.
| trace level: error
| line: 0xb957662f70a242f
| file: e:\327\enterprise\service\impl\server.cpp:678
| function: Core::ServerImpl::StartNetworkServer
| $module: mms_vsa64_12420
| error 0x30002: CannotBind
| line: 0xe6f03fbb500414fa
| file: e:\327\enterprise\common\async_ipc\async\io_base_libevent.cpp:371
| function: AsyncIpc::Libevent::IoBase::Activate
| $module: asyncipc_vsa64_12420


User wants to manually delete a .tib/.tibx backup archive in Explorer, or to modify Acronis configuration files, e.g. to adjust settings of alerts or change default ports for services.

Operation fails with “Access denied” error:

Folder access denied
You need permission to perform this action


Access to Acronis files may be denied by Acronis Self-Protection.


  1. You try to install Acronis Backup on your Debian machine.
  2. You cannot install neither 64-bit version, nor 32-bit version of Acronis Backup.
  3. Installation fails with :

    Please use installer compatible with x86_64 OS.


You try to install Acronis Cyber Backup 12.5 or Acronis Cyber Protect 15 on a machine where a NIC is disconnected or missing. Both Management Server and Agent are selected for installation.

At 99% of installation progress you get an error:

Registration failed.

Backup agent: "Failed to connect to the management server"

Manual registration fails with an error: ZmqGW return empty AMS addresses list


Issue in the product.


You created a WinPE-based bootable media.

When you boot a machine with Windows 8 or later, or Windows Server 2012 or later with this bootable media, Disk Management option is missing. 


This is the expected behavior.

WinPE-based media supports Disk Management utility for Windows 7 and below. Disk management for Windows 8 and 10, and Windows Server 2012 or later is not supported in WinPE of Acronis Cyber Backup 12.5 and Acronis Cyber Protect 15.


  1. You want to update several Hyper-V agents at once under Settings - Agents,
  2. When you select required agent machines, the following error is displayed:

More than one Agent for Hyper-V is selected. Simultaneous update of multiple Agents for Hyper-V is not possible. Please update these agents one by one.

You install Acronis Agent on a Linux machine. Installation completes with this error:

Failed to build the SnapAPI kernel module. Operations with disk-level backups will not be available.

In general, performance is constantly being optimized, so updating to the latest build is always recommended for the best performance of backup and other operations. 

First of all, please check out the general system requirements, described in your product documentation, to make sure that the hardware usage in your particular scenario is actually outside the normal operating parameters of our product. 

To investigate the issue with Acronis support, please collect the following diagnostic information:


  1. When you try to manage licenses in Settings > Licenses, nothing happens. The interface just blinks, and the license is not assigned or revoked. No error message is shown. 
  2. Protection plans are executed as if the licenses were assigned correctly.
  3. In the account_server.log (located in \ProgramData\Acronis\AccountServer\Logs), you see error messages similar to the following one:


You have installed Acronis Cyber Protect 15 software and attempt to deploy Agent for Scale Computing HC3 (Virtual Appliance);

Deployment of the Agent for Scale Computing HC3 (Virtual Appliance) instantly fails with the following error:

Failed to download the virtual appliance. Check the Internet connection on host <hostname> or download the file...


The P2V migration or V2P migration of the machines with LVM can be performed only if the backup was created using the agent installed inside the virtual machine (or on physical machine) and the restore operation should be performed using Acronis Bootable Media.

If a machine has LVM volumes, keep in mind the following limitations for restoring to a different platform:

  1. You create a backup using Version 12 format.
  2. An operation with archive (e.g. applying retention rules) fails with the error message

    Failed to lock the file


  • You have upgraded your system from Acronis Cyber Backup 12.5 to Acronis Cyber Protect 15. 
  • After the upgrade, you created new protection plans. When you try to edit a newly created protection plan, there is a spinning loading circle with Reconnecting... message.

This article applies to:

  • All Acronis software


  1. You are installing Acronis software in Windows
  2. Installation fails with:
    The Windows Installer Service could not be accessed. This can occur if the Windows Installer is not correctly installed. Contact your support personnel for assistance.


Issue in the Windows Installer.

You have upgraded from Acronis Backup Advanced 12.5 Update 5 (build 16386) to Acronis Backup Advanced 15.

After each reboot, you get multiple alerts:

Cyber Protection (or Active Protection) service is not responding


Backup fails with: 

Unknown status