BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@booklet{EasyChair:2169,
author = {Abdelmajid Ben Hadj Salem},
title = {Definitive Proof of The abc Conjecture},
howpublished = {EasyChair Preprint 2169},
year = {EasyChair, 2020}}