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inSync Client fails to activate with incorrect header check error
inSync Client fails to activate with incorrect header check error
Updated over a week ago

This article applies to:

  • OS: All supported operating systems

  • Product edition: inSync On-Premise

Problem description

This article addresses the following issues:

  • inSync Client prompts for activation even after it is successfully installed using the IMD script with the correct IP/FQDN of the server.

  • After attempts to activate the inSync Client manually, it prompts for proxy settings even when the IP/FQDN is correct and the proxy is not available.

Activation log file locations are as follows:

  • Windows: C:\ProgramData\Druva\inSync4\users\USERNAME\logs\inSyncClientGUI.log file

  • Mac: /Users/<username>/Library/Application Support/inSync/logs/inSyncClientGUI.log file.

💡 Tip

This issue would only happen in case of single port architecture i.e. for port 443 (Backup/Sync Port).


This issue occurs when the server details do not match as it is (case sensitive) mentioned under the “Server IP / FQDN” field of the Network tab under Settings of the inSync Admin console.t

This issue occurs when the server details do not match the values mentioned under Server IP/FQDN field on the Settings > Network tab of the inSync Management Console. The server details field is case sensitive and hence must have exactly the same values.

For example, if the FQDN of the inSync Master is configured in the inSync server ( Settings > Network > Server IP / FQDN ) as TESTSERVER.LOCAL and during IMD or manual activation if the values used are testserver.local or the IP address of the server, the activation fails.

Activation succeeds only if the server URL used is TESTSERVER.LOCAL.


Log file entries:
[ERROR] Connect2: error while connecting to server: <IP_Address or FQDN> Error: Error -3 while decompressing data: incorrect header check.


[ERROR] [IMD] Auto-deployment failed, could not connect to server Error -3 while decompressing data: incorrect header check.


Perform the following steps to resolve this issue:

  1. Login to the inSync Management Console and go to Manage > Settings > Network tab.

  2. Check the server address (IP or FQDN) exactly as configured under the Server IP / FQDN.

  3. Note the published IP / FQDN address of the server exactly as displayed.

  4. Edit the IMD script and change the SERVERLIST parameter with the noted IP / FQDN of the server.

  5. Use the IP/FQDN as noted while activating the inSync Client manually.

💡 Tip

For mass deployment on Mac devices, you need to update the ADDRESS parameter in the inSyncConfig.ini file.

See also

Refer the steps under the Install inSync on Mac laptops from the following article: Install inSync Client through integrated mass deployment.

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