I remembered I was curious about the HSF installation.
I see that this is on a Asus board, but I wonder if the installation for the HSF would be similar or same. This was off another post I did for aother person.
I did end up finding a PDF on an MSI installation here:
CPU-Installation PDF
Now I don't know if the steps are the same, or different for other MBs.
Pushing as hard as you can, to me is kind of insane (even though some people seemed to get it done that way), but what I'd like to point out is the locking of the hooks. If the hooks are locked into place, but if you don't verify, from the back (step 12), I guess that is where the loud snap or pop sound is coming from when pushing on them, one at a time. (from OlegusTT quote)
The instructions from the PDF are:
10. Align the holes on the mainboard with the
heatsink first. Push down the fan/heatsink until
its four clips get wedged into the holes of
the mainboard.
11. Press the four hooks down to fasten the fan.
Then rotate the locking switch (refer to the correct
direction marked on it) to lock the hooks.
12. Turn over the mainboard to confirm that the clipends
are correctly inserted.
So, I think pushing as hard as you can, might break the bottom clip that goes through the hole if your not careful. And if that is broken, that may be one reason why one pin isn't holding it down correctly.