Your three objective functions are t(1)(x(1) - x(4)),..., and your second condition contains the equations t(1)(x(1) - x(4)) = 0,...
So how can you expect to minimize anything? You have already constrained the objectives to all be zero, whatever the variables are.
Furthermore, the second equation can be solved to say x(1) = ±1, x(2) = ±2, and x(3) = ±3. So what is there to plot? What is there to compute?
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