Hello leif-perjus, Welcome to the forums ! :)
It is always a good idea to provide a link to a page that shows exactly the specs of your system. I searched for it and two pages show two different types of RAM -
http://www.cnet.com/laptops/asus-eee...-34168005.html says it has a 1 GB DDR2
667 MHz RAM
http://www.pcworld.com/product/66458...-ghz-blue.html says it has a 1GB DDR3
1333 MHz RAM
Which one is yours?
And how did you try to upgrade? Did you make sure the RAM is of same specs as supported by your netbook's slot (frequence, voltage)?
Was it a single module of 4GB or 2x2GB modules?
What did you do with the stock RAM module that came with it?
Can you access the BIOS settings?
Try inserting the original module and make sure it is properly seated. If it is under warranty, it is probably the best idea to take it to the service center to do the upgrade/fix.