Acronis Cyber Protect Cloud, Acronis Cyber Backup 12.5: Backup fails with AGENT_CORE error "A socket operation was attempted to an unreachable network"

Symptoms

Backup or another activity fails with the following error:

 {"domain":"AGENT_CORE","code":"INTERNAL_ERROR","debug":{"msg":"Post https://dc-cloud.acronis.com/bc/idp/token: dial tcp x.x.x.x:443: connectex: A socket operation was attempted to an unreachable network."}}"

Cause

Network issues. Exact cause requires investigation.

Troubleshooting

1. This error often indicates problems with network interface controller (NIC): make sure that it is functioning correctly and the network is available;
2. Run Connection Verification Tool on affected agent machine and check that all required ports are open: see Acronis Cyber Protect Cloud and Acronis Cyber Backup 12/12.5: Connection Verification Tool

Collect information

If suggested steps did not help resolve the issue, collect the following information and contact Acronis Customer Central:

1. Output of Connection Verification Tool (take a screenshot with the result of the connection check or save the results to a text file)
2. System report from the affected agent machine:
   • Acronis Cyber Protect Cloud: see Collecting system report
   • Acronis Cyber Backup 12.5: see Collecting system information