Its not showing any LED codes at all when you're trying? If its just dead, sounds like BEC that powers the esc internally has gone out. You could try bypassing the BEC if you have an external one.

Another thought - on/off switches on these can be flaky - maybe try direct connection to bypass switch? Call Castle and make sure that doesn't void any warranty you may have. They may have some suggestions to help.

http://www.castlecreations.com/support/contact.html