Brakes Stopped Working... Help!

If there is fluid in the master cylinder and all of the brake lines are intact that leaves only the master cylinder as bad. They can and do fail. Easy to fix just remember to bench bleed it first then bleed all the lines. Brakes are quite simple and there are only a few things that can go wrong. Make sure that you don't have any leaks before you replace the master cylinder. leaks aren't always obvious.