You havent shown the solver output. But my guess is that CVX’s Successive Approximation was used, and it failed, as it often does. It may also be the case that the numerical scaling of the input data is bad.
Use CVX 2.2 with Mosek 10.x or 9.x if available. Otherwise, follow the directions at CVXQUAD: How to use CVXQUAD's Pade Approximant instead of CVX's unreliable Successive Approximation for GP mode, log, exp, entr, rel_entr, kl_div, log_det, det_rootn, exponential cone. CVXQUAD's Quantum (Matrix) Entropy & Matrix Log related functions .