Mine were hard to get back on as well. Pressing them didn't work. I placed the needle on the peg, laid a small piece of soft suede leather over the center of it (to act as a buffer of sorts) and then took the rubber handle of a screw driver and ever so gently tapped on it until it went on. Several VERY SMALL taps... don't wail on it!
Oh yeah, make sure when you tap on it, be sure you're tapping it square on the "head."