Description:
Modelsim will produce this error when it cannot find a design to be loaded.
Error: "# ** Error: (vsim-3170) Could not find './work.StimModule_Unknown'."
Workaround:
To workaround this, user required to check the module name at the top level instance in the testbench is proper. Also, make sure that the module name preceeds the instance name. i.e.:module_name instance_name (PIN CONNECTIONS);