I found out the issue. Now to find a work-around.
My template (Themify iTheme2) provides a hook system to inject HTML/shortcodes/whatever and provides the ability to set it for different conditions/taxonomies. I used that to inject the mashup code and a little blurb of text into the “content_start” hook location with a condition to only show on the homepage. Like I said, everything else is working with the map except it’s not changing the POI names to the post titles and linking them as set in the master settings.
The kicker is, if I add a mashup map with the widget block, it works just fine. I just don’t have any way to make a widget block look good and work for my purposes. The hook approach I’m using does what I want but is apparently breaking that part of the MapPress plugins’ features.
Now I guess I need to get creative and find another way to add that mashup as the #1 content on my homepage ONLY. That or I’d be willing to pay/donate for some assistance getting the mashup to inject perfectly with the hook system.