Max has a few different ways to generate renders. Some of them pull their file format and weather it renders a single frame or a range, from Render Setup Window (0) even if you aren't using it to render you still have to set those options, COMPLETELY backwards and broken but its not surprising... Also if you are rendering…
I've dealt with the same issue not to long ago. It was frustrating as heck to find out that the hours rendering only produced 1 frame or not even close to the final range it was set at. This only happened when i tried to render to a video format. So to alleviate this issue i just started rendering to image sequences, png,…