New side mirror glass wont "snap" back in

[jpilk99]

I bought new glass for the drivers side mirror and can't get it to "clip" in. I easily popped the old one out. Took of the black circular plastic ring that clicks onto the back of the mirror. Plug in my heater wires ...but for the life of me can't get the new setup to clip back in. I've lined up the bottom one, at six-oclock if you will, (as I can see that whilst pushing the mirror in) but have tried 30 or so times and just can't get the other 3 clips, at 12, 3 and 9 oclock to snap in. I'm looking square-on at the mirror as it goes in, to make sure it's level and equi-distant from all side. I even took the circular "base" off the mirror, which helped to line everything up and see where I'm going, but still can't get it to snap it.

Getting frustrated.

If someone can point out what I'm missin, I'd love it. Thank you.