How do I reinstall CS4, as my serial number from CDs (and my Adobe account) is rejected?

I have CS4 Production Premium.  My PC computer died and I have to reinstall CS4 on a new computer.  I have the serial number on the CD packet (confirmed on my Adobe Account using my Adobe ID), but the program rejects this with a red cross. I have loaded the program but obviously it is merely on Trial status at this stage.  I should be very grateful to receive help in activating this product.