Disciplined convex programming error for a convex problem

1

Hello
I have the following optimization problem on CVX and I get an error:
Error using .* (line 53)
Disciplined convex programming error:
Invalid operation: {convex} .* {positive convex}

Error in cvx_optimization (line 6)
F=-(1+c1+c2.(1-theta1)).(N0+c3.*theta1).*inv_pos(N0+c4+c3.*theta1);

Error in optimization_option_two (line 235)
[x] = cvx_optimization( A,B,C,D,Bd,Cd,N0,c1,c2,c3,c4)

cvx_begin
variable theta1
F=-(1+c1+c2.(1-theta1)).(N0+c3.*theta1).*inv_pos(N0+c4+c3.*theta1);
minimize( F )
subject to
theta1>0 && theta1 < 1;
cvx_end

Can anyone please help me to know how to fix it?
Thank you so much!

2

Do you recall the linear-fractional advice from your previous question? Error using .* (line 173) Disciplined convex programming error: Cannot perform the operation: {real affine} .* {convex}