My serial number does not work.

I am putting LR5 on my new computer.  I bought this as an upgrade  That serial number works but when I put the original Lightroom 3 serial number in, it has a red X  by it.  I hit enter and goes to LR5.  But every time I close it, it will ask me to reenter all my passwords.  Been dealing with this for a week.  Can't contact Adobe.  I would love to use my new computer.  Help!