This has been the issue that has haunted ATV/UTV owners sense the beginning. The shear act of removal requires the clip on the end to not only be in the right position to collapse, but that two other conditions also exist...well..as you see..actually three. One- that when pushed in there is sufficient distance from the clip and that land on the carrier for enough movement to generate the force required to collapse the clip, Two-that the manufacturer has beveled the landing edge enough to cause the collapse..which CFM doesn't always, and three, the outer parts can take the slide hammer effect it takes to preform this action...and when they don't, you have your situation to start with. Normally, with a complete axle, you would push in hard and give it a quick and decisive pop outward, then if not released push in hard again, rotate 1/4 turn and try again. You would do this until the clip finds the correct position and finally collapses. Unfortunately, Chinese metallurgy is more often softer and tends to allow the clip to imprint or dent against the landing which makes it impossible to ever collapse so rule #1, don't slam it too hard when trying and rotating. Otherwise you will have to do as I did and break the clip off to get it out.
Ok, for you, if you can re-assemble it with stretching-out the clip enough to hold it in, do so and preform the normal routine. If not, there are some slide hammer adapters that will clamp onto it and allow you to use one. Remember to do the same push in, rotate and pop-out action. Just use the slide hammer as you would the complete axle. When and if all else fails, use the slide hammer as a slide hammer and break the clip. Part will come out..but the parts the is sheared over the outer end will be inside the diff. That's another story for another day. Good luck.