The cation does not converge either, nor does the triplet ROHF anion. (tried both with AVDZ and 6-31G)
Also, on this system SOSCF is completely useless. I tried using it, but whenever the density RMS got low enough for it to start doing anything, it never managed to converge the microiterations. When I gave it 100 microiterations, the SOSCF just diverged to infinity.