Sorry, no answers but lots of questions.
1. What is the version of RoboHelp? 8, 9, 10, 11, 2015 Release)?
2. What is the output type? (WebHelp, Responsive HTML 5, Multiscreen, CHM)?
3. How are they attempting to view the output? (By pressing F1 in an application, double-clicking a file somewhere?)
4. Where is the output when they try to view it? (Local PC, Company Intranet, On the Web?)
We see this issue with our RH9 help, when viewed in newer browsers, like IE11. Moving to RH2015 fixes the problem. We did have to make a point of removing the old eHlpDhtm.js files from the project source files, too.