3DS Max 2014 Vray Next update 3.1
Just installed Forest Pack Pro 6.2.3
Same problem with Forest Pack Pro as Alfa Smyrna. However, their suggestion of switching the Render mode to Meshes instead of the default Automatic, does not work. I tried it
What I have discovered what does work, with any scene that uses FP., The FP objects do not render if using IPR. However if you instead hit Render, FP objects render perfectly.
IPR was working fine in 6.2.2 and it's incredibly useful and you can even move FP objects around, interactively. Something that (obviously) isn't possible, if the FP objects do not rendering with IPR. While I know IPR is not the ideal way to render a scene with FP and certainly not with Railcone as interactivity of any sort, is just not possible with Railcone and IPR, I do find it most annoying, that everything was working fine with IPR and now this.
So my guess is, whatever you did that "Added specific support for V-Ray 4.3" is the problem, because as far as I could tell, it was working just fine with 4.3, until now of course.
While IPR might not be to everyone's liking, it is a vital part of my workflow and I imagine many others too, so hopefully you can get this sorted ASAP