Several factors can cause a connection issue:

• Network problem
• Crucial services are not installed
• Services not started
• Firewall issue

Follow these steps to troubleshoot connection issues:

1. Check for known issues in the Known issues part.
2. Follow to Troubleshooting part to troubleshoot and resolve the issue.

Known Issues

Acronis Backup Advanced 11.5: Connection to Agent Fails with "The requested license holder cannot be found"

Acronis Backup Advanced: Connection Errors Out with "Failed to create the channel" or "SSL Connection Failed"

Acronis Backup Advanced: Connection Errors Out with "Required Service is Unavailable" and Error Code 0x00AD0003+0x00030431

Acronis SharePoint Explorer: Console Connection to the Agent Fails with "Failed to initialize local farm"

Acronis Backup Advanced: Unable to Connect to Acronis Management Server after Update

Troubleshooting

Follow step-by-step instructions below to troubleshoot the issue. Complete prerequisites step before proceeding to error troubleshooting step.

Prerequisites

Complete all steps before proceeding to error troubleshooting step.

1. Check your Acronis Backup edition

Connection between components is allowed in the following editions:

• Acronis Backup Advanced for PC
• Acronis Backup Advanced for Windows Server
• Acronis Backup Advanced for Linux Server
• Acronis Backup Advanced for Exchange
• Acronis Backup Advanced for SQL
• Acronis Backup Advanced for SharePoint
• Acronis Backup Advanced for Active Directory
• Acronis Backup Advanced for VMware / Hyper-V / RHEV / Citrix XenServer / Oracle
• Acronis Backup for Windows Server Essentials 

Trying to connect to another Acronis Backup product will fail with event code 0x00AF0010 and error message"Failed to establish remote connection: Remote connections are disabled."

2. Check installed components

On a Windows or Linux Agent machine Agent Core and Acronis Agent for Windows/Acronis Agent for Linux should be installed.

On a VMware ESX(i) host Acronis Virtual Appliance should be installed.

On a Hyper-V host Agent Core and Agent for Hyper-V should be installed.

Otherwise connection will fail with event code 0x00AD0003+0x00030431 and error message "The required service is unavailable on the remote machine."

Or with event code 0x00AA0021 and error message "Only Acronis Agent Core is installed."

3. Check user and credentials

Credentials you are trying to connect under should be correct and belong to a user, who is a member of Acronis Remote Users on the target machine.

Add permissions as deribed in Acronis Backup: Required User Permissions for Local and Remote Management

Otherwise connection will fail with event code 0x00AF0006 and error message "Failed to establish connection using the specified credentials".

Or event code 0x01140013+0x01140013+0x00AD0003+0x00AD0003+0x00040014+0x00030436 and error message "Failed to connect to the agent on remote machine".

4. Configuring Acronis Backup for multihomed environments

Should you have Acronis components installed in different networks, configure as described in these articles:

Acronis Backup Advanced: Settings for Multihomed Environment

Acronis Backup Advanced: Configuring Communication between Components Placed behind NAT

If all steps above have been executed and issue still persists, go to error troubleshooting step.

Error troubleshooting

Complete all steps before proceeding to collect information step.

Check whether Acronis components work properly on the remote machine:

1. Make sure the required components are installed on the machine you are connecting to.
2. Make sure the respective service as well as Acronis Remote Agent Service are running, see Acronis Backup 11.7/11.5: Windows Services and Processes. If a service is not running or stops/crashes after startup, please refer to Acronis Software: Troubleshooting Application Crashes
3. Make sure the service is not hanging. Check it in one of these ways:

• connect to it using Acronis Management Console on the same machine;
• on the machine, open the Command prompt (Start -> Run -> cmd) and issue acrocmd list disks if you do not have console;
• on the machine, use telnet to test if the port is open. Acronis uses port 9876 for communication between components. Open the Command prompt (Start -> Run -> cmd) and issue telnet <hostname/ip> 9876 where <hostname/ip> is the name or the IP address of your machine.
  If the above steps fail, the component hangs. Please refer to Acronis Software: Troubleshooting Application Lockups

If the above three steps succeed, you are facing a network issue. Please follow these steps to troubleshoot network-related issues:

1. Use nslookup to check if the hostname of the machine is resolved into correct IP: Open the Command prompt (Start -> Run -> cmd) and issue nslookup <hostname> where <hostname> is the name of the remote machine.
   If that fails, you are facing a DNS issue. Solve it or use IP addresses instead of DNS names.
2. Use ping to check if the remote machine is reachable. Open the Command prompt and issue ping <hostname/IP> where <hostname/IP> is the name or the IP address of the remote machine.
3. Sometimes ICMP packets are blocked by firewalls. Try to perform some remote operation with the machine: e.g. open a share on the machine or RDP to it. If such an action fails, connection is blocked on the network-level.
4. On a Windows Machine use telnet to check if the port is open. Acronis uses port 9876 for communication between components. Open the Command prompt and issue telnet hostname/ip 9876 where <hostname/ip> is the name or the IP address of the remote machine.
   If telnet fails that means that the ports are closed on the target machine or between the machines. Use this article to open ports: Firewall settings for Acronis products.
   Linux machines usually use “iptables” firewall. You can allow the traffic through port 9876 by issuing the following command:
   sudo iptables -A INPUT -p tcp --dport 9876 -j ACCEPT
5. If all above was performed but the connection is still not established try solution 2 and 3 from this article

If all steps above have been executed and the issue still persists, go to collect information step.

Collect information

Collect following information and contact Acronis Customer Central.

1. Telnet
Screenshots of telnet output.

2. Network tracing log
Reproduce the issue and collect a network tracing log using Wireshark.

3. Process monitor log
Reproduce the issue and collect a Process Monitor log.

4. System report
Collect System Report from both machines in question: see instruction for Acronis Backup 11.7/11.5: Generating System Report, if this fails for any reason, you can use this AcronisInfo Utility