Error: [Signature download for 'user@domain.com' has failed on attempt 1. Retrying after 00:10:00. An error occurred while sending the request] – Exclaimer Cloud

Scenario

You have installed Exclaimer Cloud Signature Update Agent via the Click Once installer and this error is visible in the logs when the signatures have not synced:

ERROR: Signature download for 'user@domain.com' has failed on attempt 1. Retrying after 00:10:00. An error occurred while sending the request.

Reason

The Windows update KB4520405 (KB4519565) has made a change to Windows that affects the default protocols used by the Click Once applications and forces them to utilize the Transport Layer Security (TLS) 1.0. This method has been deprecated and therefore causes the agent to not connect.

Resolution

To resolve this issue, edit the registry values to enforce the usage of TLS 1.2 on the machine where the issue has occurred.

WARNING! Windows Registry modifications should always be approached with extreme care - serious problems can occur if you modify the Windows registry incorrectly!

We strongly advise you to back up the Windows registry before any modifications are made - in doing so you will have the option to restore the backup if a problem occurs.

For more information, see How to back up and restore the registry in Windows.

Please click on the required options listed below to go through the detailed description:

Enable the TLS protocols on the machine

Launch the RegEdit (Registry Editor).
Browse to the following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols
Right-click the Protocols folder and create a new key called TLS 1.2.
Right-click the (new) TLS 1.2 key and create a new key called Client.
Right-click the (new) Client key and create a new DWORD (32-bit) value called DisabledByDefault.
Set the value of the DWORD to 0 and the Base to Hexadecimal.

Enable the SchUseStrongCrypto property in the Windows registry

Launch the RegEdit (Registry Editor).
Browse to the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NetFramework\v4.0.30319
Right-click the v4.0.30319 key and create a new DWORD (32-bit) value called SchUseStrongCrypto.
Set the value of the DWORD to 1 and the Base is Hexadecimal.
Repeat steps 3 and 4 for the following key:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319

Once these keys have been updated, reboot the computer for the changes to take effect.

If you do not wish to make changes to the registry, you can deploy the MSI installer using Group Policy. For more information, see how you can deploy Exclaimer Cloud Signature Update Agent via Group Policy Object (GPO).