I need to update a user guide I created but the project file was either deleted or misplaced. Am I able to somehow convert the HTML5 output and reload back into RH or at this point will I need to create an entirely new project and just copy/paste the pages manually? Running version 10 by the way.
You need to “reverse engineer” your output back into a RH project – see Willam’s site – www.wvanweelden.eu
As Jeff remarks, you need to reverse engineer your output. At this time, I offer scripts for automatically reverse engineering WebHelp, CHM, FlashHelp and AIR. Unfortunately, at this time, I don't have an automated option for Multiscreen HTML5/Responsive HTML5.
If you are using an HTML5 output, for now you're stuck with manually recreating the project. Check out June 2004 - Impure Sorcery on some info on how this process works with WebHelp. For HTML5, I suggest creating a blank project and copying the content from the browser as you need to clean up much more than with WebHelp.