Did the leaves fall off? Something not working right? Let us know how we can improve the Photosynth experience.
Using Win8.1, IE11 desktop. There are plenty of Synths not showing here http://www.bing.com/maps/?v=2&cp=12.106258~-68.935815&lvl=19&dir=0&sty=a&app=6793~ps~~dtpfilter~All~poi~Normal&FORM=LMLTCC
For quite a few years now, Photosynth's Bing Maps App doesn't show every synth in a given area on the map, but rather only those which it considers to be synthy enough. Also, any unlisted synth will never appear on the map or in search (it may appear in web search results if someone posts a link to it on the public web somewhere).
If these are Photosynth 1 synths, what happens when you view them on Photosynth.net and click the map link on the lower left of the page? Do you get their pushpin highlighted in the Map App or is that link still broken since http://bing.com/maps/explore was taken down?