In project Setup under Windows there will be new window. If the microsoft html help is primary layout (else make it primary layout) then double click new window and check Browse Sequence in the bottom left corner.
Then click tools > Browse Sequence Editor and you can add the desired topics that you want else you can click Auto creating toc at the bottom if you want to add the entire topics under toc
Then generate the CHM and observe it is working for you or not.
Hope it helps
Perhaps you need to register the 64 bit version of HHActiveX.dll?
My thought here is that perhaps you are using a 64 bit Windows system. And when that's the case and you launch the CHM from RoboHelp, you are actually launching the 32 bit version of the CHM viewer. But when you simply double-click a CHM file to open it up from Windows Explorer, you are usually launching the 64 bit version of the CHM viewer. So if the 64 bit version of HHActiveX.DLL isn't found, you aren't seeing the Browse Sequences or the Glossary Tab as those rely on this file.
Check the thread linked below for info that may help.
Registering the 64 bit version of HHActiveX.dll solved the problem. Thanks for the help.