help cvx/norm --> norm is nonmonotonic, so its input must be affine. help cvx/log --> log(X) is concave and nondecreasing in X. When used in CVX expressions, X must be concave. Also, read FAQ: Why doesn’t CVX accept my problem? [READ THIS FIRST]

can you please explain why I can’t multiply a matrix with absolute value of an unknown variable in a norm expression? Is it not an affine expression or due to being monotonic? I know that it is my responsibility to ensure my problem is convex but I cannot understand the constant matrix error. Thanks

I agree the second error message is cryptic. Handling error messages correctly is one of the harder things to do in software like this, because of course you’re having to anticipate all the wrong ways people use your software. That said, you are simply not heeding the FAQ. You need to read it.