If you use a LS-DYNA inputfile that contains *CASE keywords in LS-OPT, you have to specify the Subcase field in the response or history definitions. The Subcase is the integer CASE ID associated with the *CASE parameter in LS-DYNA. This field is mandatory for disciplines that use *CASE parameter in LS-DYNA input files.
For details, see LS-OPT Manual, section History and Response Results.