Did you ever resolve this?  Our research suggests that it was a Microsoft Patch in May that broke the registry solutions which Vanessa provided, and which used to work.

I ran into the same issue. Sage is researching a solution and has not found one yet.

When previous Sage300 Help problems were caused by Windows updates, fixes including MaxAllowedZone, UrlAllowList and Trusted Sites worked, but this new Windows Update has stopped them working.

Microsoft acknowledges the problem is caused by their decision to stop access to HTML help files over a network location, but has not committed to solve it, so it's up to Sage to change the way their Help works:

https://social.technet.microsoft.com/Forums/en-US/dc9ae58e-4218-4dd3-8b72-3b32a5b3d874/can-no-longer-open-chm-files-across-the-local-network-after-installing-cu-for-windows-1709-for-x64?forum=ieitprocurrentver

Anyone got any other ideas apart from the nightmare-inducing full install on every workstation?

Workaround:

Copy the Help folder to the same local disk address on each workstation or term server (eg C:\Install\Help)

In each company, on the Sage 300 desktop, add an "all users"  shortcut to System Manager Help (C:\Install\Help\SM64AENG.CHM)

 It doesn’t fix F1, but at least users can access Help, and System Manager Help finds Help for all modules.

Sage say this is fixed in Sage 300 2017 PU7 and Sage 300 2018 PU3