I went to Iceland in December and was given a Nikon D5500 as an unexpected Xmas gift (I've always been interested in photography, but never learnt anything formally). I tried to Google how to set up my camera before going to see the lights but my images are still black (there was no clouds but the lights were not very good anyway). I was hoping that some kind of editing might help? I am going back next year hopefully more prepared!
As you have the RAW file, try this :
Get an application that can process RAW. If you don't have one (e.g. LightRoom) try the free RawTherapee which is a very comprehensive RAW developer.
In the application open your RAW file
There will be a way to adjust exposure, typically a slider with a scale going from (e.g.) -3EV to +3EV. Slide it all the to the right (positive side).
There are other adjustments you can try (tone curve, gamma) if that fails.
That will brighten the image and if there's anything there you should see it.