V-ray GPU won't render with Render Button in Render Setup

[LeeJ]

Hi, I have Vray GPU Next selected as my renderer in the Render Setup window. If I click the Render button, the VFB opens, and the status bar stops at "Preparing scene for rendering....: Done [00:00:00.0]" The VFB stays black, and nothing else happens. In the VFB, if I click "Render Last", it will render the scene. Also, if I click "Start Interactive Rendering" button, it will render as expected. Any ideas why the Render button might not be working? I've restarted 3ds Max, but still having the issue.

Thanks