Advance have issued an advice notice for all customers experiencing issues with the help files within Exchequer.The following knowledgebase (KB) articles from Microsoft have the fix for .chm files. 

Operating System Resolving KB
1803 / RS4 Windows 10 KB4458469
1709 / RS3 Windows 10      KB4457136
1703 / RS2 Windows 10         KB4457141
RS1 Windows 10                    KB4457127
TH2 Windows 10                    KB4457130
TH1 / RTM Windows 10          KB4457132
Windows 8.1/ WS12R2          KB4457133
Windows Server 2012 KB4458469
Windows 7 / W2K8 R2      KB4457139
Windows Server 2008            KB4458469

The knowledge base articles can be found at support.microsoft.com/en-gb       

If you need any further assistance or advice, please contact us on 01707 607100 or by emailing contactus@minervauk.com.