use a blowdryer - only way I could get them to snap into place easily.
Which end ? Male or female?
I blowdried both ends for about 20 seconds each. that should do it.
try not to heat up the rubber , pull it back a little first.
I blew the female end on mine and it popped right in...don't blow to much though,..just enough to get the job done....hold the male end to keep the rubber from sliding down and gently but firmly push the female end right on...works like a charm...
Have you ever heard of Finbar Saunders?