Gently remove and clean (with a pencil eraser) and reinstall your memory, then try again.
For you non-techies, it is very easy to hose a perfectly good laptop by
NOT fully releasing the side-latches (some metal, some plastic) BEFORE
gently lifting the RAM up 1/4", away from the pin/contact seating area,
and OUT of the sockets. Actually, if you do it right and do not
physically touch the face, sides or corners of the RAM when you use
your Left and Right thumbnails to 'tease' the latches away from the
sides of the RAM, it will POP out all by itself.

Now... putting new RAM in is REALLY easy and does not require any force
or pressure at all. Look at the socket and the RAM and orient your RAM
so the slot in it (the RAM) and the raised portion of plastic in the
contact seating area line up. If it is OBVIOUSLY not, flip the RAM over
and check again. If it still will not, or can not line up... it is the
wrong type RAM for your machine. Take it back. Do not try to 'make it
fit' ;-)
Once you have RAM oriented so it WILL slot in, take the RAM between
your index fingers and thumbs so the contacts are facing AWAY from you
and hold firmly by putting the tips of your fingers into the holes on
the sides of the RAM, ease the RAM into the socket and seating area,
wiggle a bit side to side and seat in snugly, then maintaining the hold
with your 2 Thumbs, tease the latches away from the socket edges with
your fingernails (under the edges of the new RAM) so they both clear
the sides of that RAM, then gently press down a bit further with your
thumbs until the RAM face is below the latches and finally release the
latches making sure BOTH are now above the RAM face. Done.
Don't FORCE... EVER ;-)
Hope that helps