Advice: Do not use quiet, expert, or turn off warnings until everything is working well.
Have you proven that your problem is convex? Please read Why isn't CVX accepting my model? READ THIS FIRST! . I will mark the problem as non-convex until such time as you prove that it is convex. I don’t like doing that,because the expression in the thread title is convex, presuming that x and t are CVX (optimization) variables, and marking the thread as non-convex seems to imply otherwise.