Make sure you are using CVX 2.2.2 or CVX 2.2. Do not use CVX 3.0beta, which is riddled with bugs. It’s possible your MATLAB session was corrupted.
In any event, if you have Mosek available as solver, use it.
Otherwise, follow the instructions 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 .