I've come across a lot of people who play Banjo really well but can't transcribe songs for them selves. Many have tried and failed, usually when they started playing, and since then have been convinced they don't have "the ear" for it. Thing is that 99% of them are wrong! If you can play a song from start to finish and know you haven't played a wrong note, or can tell if your Banjo is out of tune, then you have a good enough ear to work out simple to intermediate songs and beyond.
However I will agree that it doesn't come naturally to us all, and like our playing, it can take time to develop. It certainly took me several years of occasionally trying and to varying degrees failing before I was able to transcribe songs myself, and to help you speed up this process I am going to share some advice.