How do I fix peeling, pre-mixed epoxy paint on my garage floor?

Last summer we used one of those DIY garage floor pre-mixed epoxy paint kits, and despite our carefully following the provided instructions to prep the garage floor, it almost immediately started to bubble and lift off the concrete in areas. Now what? How do we proceed now? Try to scrape off what we can and reapply over the entire floor? Is there still hope that we can complete the project ourselves OR ???