b92e5fe91b32789c990e4ac8c54f5a01.jpgTry "lightly" tapping it into place with small punch. If it don't go don't force it. I have had wrist pin snap rings be stubborn at times. Next step would be to call Weisco; they make different styles and thickness ones. Both flat and round wire.
I actually used to use teflon buttons on my wrist pins.