Inspiron 5505, issue adding 8GB RAM

I received my Inspiron 5505 today.  Initial laptop config and account setup, it works fine.  I then tried to add another 8GB RAM.  After adding the RAM the laptop detected it correctly.  However, i notice that the touchpad "tapping" function stopped working.  I then removed the newly added RAM and it started working again.  Therefore I thought the touchpad "click" issue was somehow caused by faulty RAM.  I then continue to upgrade the laptop with the latest Microsoft security patches as well as Dell Bios upgrade(to v1.4.0) and some driver updates.  After the Bios was updated and machine rebooted, I notice that the touchpad stopped working again.  This time not only it does not respond to "tapping", but it does not move the pointer either.  I have tried to follow another user's suggestion of removing the back cover and try again.  However, it did not work for me.  I am wondering if anyone else has any other suggestion?  This is a Christmas gift and I really hate to return it 1 day before Christmas.