There has been recent discussion on midrange.com of RDi online help not working due to IBM switching access to the https protocol. Can this be fixed by Window > Preferences > Help > Content, then choose a remote help URL, Click Edit Change http to https, Click OK?
As I'm on version 9.5.0 which seems to search for local help, I used this page to install local help. This allows me to see help documents in RDi using Help, Help Contents but still takes a very long time to respond and display the page. As far as I can tell, there is no preference to disable local help.