I made a light beam, very similar to this: https://cloud.blender.org/p/caminandes-3/56c6da5cc379cf0079716873, but for some reason I can't render it. If I switch to rendered view mode, I see everything in place, but when I render it, there's nothing in place of the beam, except for some lighter and yellower rain drops. on the top half, you can see 3d rendered view mode, on the bottom half, you can see actual rendered image. I have checked in outliner, that everything should render (which is also visible from the image). Here is my nodesetup: I am using cycles render.
There is likely nothing wrong with your setup.
The issue is with the render viewport not being able to display emissive and transparent pixels.
To check this try either
or compositing your image over some color (or black) background,
or simply looking at the RGB image with no alpha on the viewer.