No, you can install it on two computers, so that's not it. Are you sure you're entering it correctly and that you have all the digits?
Yes, I am completely sure. I have entered the digits correctly, and I have checked numerous times, but it continues to say invalid serial number. I do not understand what is happening.
I have entered it with 20 digits as the box has (XXXXXXXXXXXXXXXXXXXX). And I also checked my computer Photoshop Elements 7.0 for the serial number and it has the exact same number as the box.
The complete serial number is 24 digits. The last 4 digits are not displayed on the installed program's start-up screen.
Oh, then I must check again. Thank you for telling me.