We found that in Arcmap 10.6.1 (only one tested) on windows 10, that if you click on the Geoprocessing menu, click on any of the tools at the top of the list, then click on Show Help, then Tool Help you get this error:
Can’t reach this page
Make sure the web address //ieframe.dll/dnserrordiagoff.htm# is correct
Search for this site on Bing
Refresh the page
Check that all network cables are plugged in.
Verify that airplane mode is turned off.
Make sure your wireless switch is turned on.
See if you can connect to mobile broadband.
Restart your router.
We have found that if you apply the update KB4480976 for windows 10 1803 (after doing all updates for 1803 and not allow 1809 to be installed), that it fixes the problem. If 1809 is installed, and before or after installing updates, it is broken again. Anyone aware of a fix for 1809 that will fix this issue?