I discovered the answer when I upgraded to GMapFP Pro. The map no longer works (no idea why), but instead shows how I called GMapFP:
{gmapfp id="2,3,4,5,6,7,8,9,10,,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40"}
So, the 40 item limit was set by me, not GMapFP. User error. But now I don't see a map, just the {gmapfp id=" "} code. Should I switch back to the free version?