You say that you cannot launch RoboHelp but you go onto to say that opening with the HHP file fails. How are you openng the HHP file if you cannot start RoboHelp?
I think in your situation would be uninstalling RoboHelp, rebooting and then reinstalling RoboHelp. It is simple enough and will not affect any existing projects. Before trying to open any projects, apply the updates to Version 11. Apply Update 4 as the earlier updates are included.
Let us know whether or not that changes things. Especially if you can then at least open RoboHelp as there's more to try.