Hi Fardin and welcome to our community
If memory serves me on this one, you need to do the
following.
1. Close RoboHelp
2. From Windows Explorer, locate a .HTM file
3. Right-click the .HTM file and choose to Edit With Internet
Explorer
4. Allow Internet Explorer to open, then close it
5. Restart RoboHelp and see if things have improved
Give that a go and see how you fare.
Cheers... Rick