  Gap opening remains elusive in copper chalcogenides (Cu$_{2}X$, $X$ = S, Se
and Te), not least because Hubbard + $U$, hybrid functional and ${GW}$ methods
have also failed. In this work, we elucidate that their failure originates from
a severe underestimation of the 4$s$-3$d$ orbital splitting of the Cu atom,
which leads to a band-order inversion in the presence of an anionic crystal
field. As a result, the Fermi energy is pinned due to symmetry, yielding an
invariant zero gap. Utilizing the hybrid pseudopotentials to correct the
underestimation on the atomic side opens up gaps of experimental magnitude in
Cu$_{2}X$, suggesting their predominantly electronic nature. Our work not only
clarifies the debate about the Cu$_{2}X$ gap, but also provides a way to
identify which of the different methods really captures the physical essence
and which is the result of error cancellation.
