This is what I was talking about in my paragraph from above
Did the solver fail to solve the problem? That is possible. To minimize the chances of that happening, make sure the problem scaling is good, use CVX 2.2 with Mosek 9.x if possible, otherwise follow the advice 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