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Purpose
Sometimes the CrashPlan app can't make a network connection even if the Internet appears to be working. This is because the CrashPlan app relies on specific ports to be open. The linked article below describes how to test connectivity on the correct ports to rule out problems with firewalls, anti-virus products, or other network issues.
Details
When troubleshooting your network connection, it is important to test all of the addresses and ports used by your CrashPlan app to connect to the CrashPlan server.
Please refer to Test your network connection for more details and step-by-step instructions.