Thanks Peter,
It was the elevation, I raised it a little at it works now. Seems that the send to surface , in general is not too reliable, I also had some trees that refuse to go to the surface in one area, even though the aeea was definitely covered by the Site Model.
After I made a pad though in that area I was able to send the trees to the surface successfully.
Do you also know a work around when Send to Surface does not work? I originally made my plan with no site model now that I added a site model I need to get everything to the surface, things like a tennis court, shelters trees etc. So far I have made a pad for a basketball court then made 3d polys for the court lines, fences and basket and pole. This technique seems to work OK.
I appreciate any advice.
I used Landmark years ago, it was very buggy. I am thrilled overall with how much better it is, but also disappointed that , it seems , send to surface is still buggy.
Of course my brand new iMac, with i7 and 32GB of ram, makes using LM/VW a pleasure compared to a Pentium 450 with windows.
Thanks again.