Do not use quiet mode until everything is running properly. Re-run the problem without quiet. What specifically happens when you run it? Your problem is not reproducible (for instance, what is channel).
Given use of log, I recommend you follow the advice in 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 .