RoboHelp 2015. Generated master project doesn't recognize subcategories in index keywords.

I have a master project that houses external links to many projects (over 70) and all index entries combine to create a master index for the help system. After I upgraded to RH2015 and I have generated both the sub-project and the master project, the keyword/subkeyword relationships have disappeared. Index entry keywords are listed without any subcatgories although the project has them. Like this:

So, now I have a giant list of keywords without the indentations to delineate the keyword groups. I did much of the index by hand using the Topic Properties and the "keyword\subkeyword" format. Has that delimiter changed? Anyone know or have the same issue? Am I missing a simple setting some place?

I've been through the What's New and Forums here, but am not seeing anything.

Thanks in advance.