Does anything happen at all when you plug your target into the PC?
What target hardware are you using - your own custom design, or an eval board or dev kit, etc? Are you sure that the application is correctly loaded and running in the target? Did the application build ''cleanly''; ie, with no errors and no warnings? What debugging have you done?
A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.