Lesliel1692659, the serial number registered under your account is for an educational version of Creative Suite 4 Design Standard for Mac OS.  If you use the retail installation files at Download Adobe Creative Suite 4 (CS4) products then you will receive the serial number is invalid.  You will need to locate the installation files that were provided with your purchase to use that serial number.  If you purchased the software from Adobe directly then see Find downloaded apps and files for details on how to download software from your account.

Please see the information provided by John in post #1 of this public forum discussion.  You must use the workarounds he has referenced to install CS4 on modern versions of Mac OS.

First, that very old program is not fully compatible with your new operating system, so you may never get it to work properly

CS6 and earlier programs have not been tested and will not be updated for Mac El Capitan or later operating systems

-which means that you try to use CS6 and earlier at YOUR risk of having problems due to Apple updates

-Apple did not maintain backward compatibility with old programs in El Capitan or Sierra

--Adobe has a workaround to Apple's problem of not maintaining backward compatibility

--READ HERE https://forums.adobe.com/thread/2301916 for an Adobe solution to installing old programs, including a link to installing the old Java runtime that is required

--Also read for more information https://forums.adobe.com/thread/2458382

If you are not installing from your original CD, did you download the installer that matches your serial number? (A Master Collection serial number will not work with any other installer)