There are three situations that can cause this error:
- You participated in a prerelease program, and the prerelease serial number is still stored on your computer. Serial numbers for prerelease programs expire when the prerelease program ends.
- You installed a trial version of the application on the computer, which has expired.
- Adobe Customer Service deactivated your serial number. This issue can occur when you request a new serial number from Adobe Customer Service.
The error "The license for this product has expired" is unrelated to the error "Licensing for this product has stopped working." An expired license means that a serial number, which is no longer valid, is still stored in the pcd.db database file. The valid serial number you received with your purchased product didn't overwrite the expired serial number during the installation process. Removing the expired serial number allows you to enter your valid serial number.
The error "Licensing for this product has stopped working" is related to the activation component of Creative Suite 4 software. It is related to a problem with the FlexNet Service. (Creative Suite 5 software uses a different activation component.) See these documents for solutions on how to resolve this particular error: