The study of the 4 -tachyon off-shell string scattering amplitude A 4 ( s , t , u ) , based on Witten’s open string field theory, reveals the existence of poles in the s -channel and associated to a continuum of complex “spins” J . The latter J belong to the Regge trajectories in the t ,  u channels which are defined by - J ( t ) = - 1 - 1 2 t = β ( t ) = 1 2 + i λ ; - J ( u ) = - 1 - 1 2 u = γ ( u ) = 1 2 - i λ , with λ = r e a l . These values of β ( t ) , γ ( u ) given by 1 2 ± i λ , respectively, coincide precisely with the location of the critical line of nontrivial Riemann zeta zeros ζ ( z n = 1 2 ± i λ n ) = 0 . It is argued that despite assigning angular momentum (spin) values J to the off-shell mass values of the external off-shell tachyons along their Regge trajectories is not physically meaningful, their net zero-spin value J ( k 1 ) + J ( k 2 ) = J ( k 3 ) + J ( k 4 ) = 0 is physically meaningful because the on-shell tachyon exchanged in the s -channel has a physically well defined zero-spin. We proceed to prove that if there were nontrivial zeta zeros (violating the Riemann Hypothesis) outside the critical line R e a l z = 1 / 2 (but inside the critical strip) these putative zeros d o n ′ t correspond to any poles of the 4 -tachyon off-shell string scattering amplitude A 4 ( s , t , u ) . We finalize with some concluding remarks on the zeros of sinh ( z ) given by z = 0 + i 2 π n , continuous spins, non-commutative geometry and other relevant topics.