Some of this will sound basic, but not sure what your mechanical skill level is. First make sure shifter Is in neutral. Check all fuses under dash. Third fuse from the top powers the ignition switch. Make sure to check them using voltage check, not ohms. Since it was running one day then nothing the next and battery is good, suspect bad key switch, broken wire, failed fuse, neutral start switch or bad cable connection at the battery. Pull the ignition switch and check wires on back. The battery connections should read battery voltage. The key switch has a wire coming off the starter connection that supplies power. With a volt meter, check power across the battery. Now put your positive lead at the positive battery post and touch the engine block, reading should be within 2 tenths of the battery reading. Switch the test leads and check the negative side. Certain switches you can jump out to test. Good Luck

Hope you have it running now, but in case you haven't: The one I'm working on had a broken wire there near the battery. I can post up a pic (I think) if you need.