? Error using ==> subsindex Function 'subsindex' is not defined for values of class 'cvx'

this is my convex problem; and here is my code.

cvx_begin
variable x(S);
variable d(N);
expression Flow_of_Link(N,N);
expression sum(1);

maximize ((-1)*sum(pow_p(((Dist_SP_BA.^2).*(x(1:S))),(-1))))

subject to 
	sum(d(1:N)) == M
	x(1:S) <= up_flow
	x(1:S) >= lb_flow
	d(1:N) >= lb_node
	Flow_of_Node*x(1:S) <= d(1:N)
	for m=1:N
		for n=1:N
			sum = 0
			for i=1:S
				if (Flow(i,4+m)==1 && Flow(i,4+n)==1 && T(m,n)==1)
					sum = sum + x(i)
				end
			end
			Flow_of_Link(m,n) = sum
			Flow_of_Link(m,n) <= T(m,n)*(1+p)*(d(m,1)+d(n,1))
		end
        end

cvx_end

However, I get error
??? Error using ==> subsindex
Function ‘subsindex’ is not defined for values of class ‘cvx’.

I changed the expression of the first constraint, and there is no error now~

My question is regarding this topic sir, my constraint is
eqation
where phi{m} is a cell array of dual variable of size m, Gamma(m) , qm (m) are given array of size m
and Pi Pj are optimization parameters
my cvx code is as,
for m = 1:10
A = sum(-Gamma_m(1,m)+ qmx(1,m).*(Pi+Pj));
phi{m}: A<=0;
end

Please show the completer code and error message.