BibTeX does not have the right entry for preprints. This is a hack for producing the correct reference:
@booklet{EasyChair:9139,
author = {Frank Vega},
title = {On the Nontrivial Zeros of the Riemann Zeta Function},
howpublished = {EasyChair Preprint 9139},
year = {EasyChair, 2022}}