re: "Unknown subcircuit called in"
I guess that means you did something wrong.? Your subcircuit call (the netlist line starting with X) refers to a subcircuit name, which was never defined.? Maybe the names don't match.? Maybe the subcircuit definition is missing.
There is also some chance that the subcircuit call has a confusing arrangement of nodenames and parameters, so that it causes LTspice to use the wrong one as the subcircuit's name.
I don't recall if we had any information (or enough information) about what you are simulating, so that we can offer more advice.? We need to see what you tried to simulate, before we can see where your mistake is.? Can you upload it?? If you do, make sure to check the instructions for uploading simulations to the group's Files.
Andy