I am trying to simulate a testbench for an opamp in xschem and I am getting this error from ngspice, I do not know what is the cause, can somebody help.

First of all voltage source v3 is not connected to anything. add a net and a label to it like you did for v1. Do not include spice models inside the subcircuit (the opamp) do this at the test bench, the top schematic. For further help attach the opamp_tb.sch and opamp.sch/opamp.sym.