I presume you mean u2= t*p2 and u3 = t*p3
As written, this is non-convex. In any event, the problem is unbounded (unless there are other constraints you haven’t shown), because p1, p2, p3 can go to infinity along with t, in order to retain feasibility.
If U1, u2, u3 were affine (or variables themselves), the constraint could be written as -rel_entr(t,u1+u2+u3)) >= 0 and would be allowed by CVX. But u1, u2, u3 are mot affine, and this constraint would therefore be rejected by CVX, whether or not in gp mode (gp mode would allow the multiplication of variables, but not what you subsequently did with them)…
In the future, please copy and past code using the Preformatted text icon, rather than posting an image of code.