Out of 44 Cp 9 files, three won't open when published in HTML. Info./design is the same across all files. Any ideas for troubleshooting would be greatly appreciated.

There should be a difference: did you look at file size, do you have video, learning interactions, animations, effects, quizzes...? Are you using 9.0.1.320?  They cannot be identical. How did you test: HTML files should be tested after uploading to a webserver or a LMS, not locally.