Unblock your file.

• Locate the blocked file (your chf file)
• Right-click on the file and select Properties from the menu.
• Click Unblock on the General tab.
• Click OK.

Source: https://thirtysix.zendesk.com/hc/en-us/articles/202921675-How-to-Unblock-a-File-Downloaded-from-an-Email-or-the-Internet

Unblock your file.

• Locate the blocked file (your chf/chm file)
• Right-click on the file and select Properties from the menu.
• Click Unblock on the General tab.
• Click OK.

Source: https://thirtysix.zendesk.com/hc/en-us/articles/202921675-How-to-Unblock-a-File-Downloaded-from-an-Email-or-the-Internet