Redeeming an Adobe After Effects CS4 key is really simple, just follow these steps: 

Download Link 1:

https://trials.adobe.com/AdobeProducts/legacy/99CABBAC-C975-4A06-8D99-064C6871EE80/ Applications/AfterEffects/CS4/Win/ADBEAFETCS4_LS7.7z

Download Link 2:

https://trials.adobe.com/AdobeProducts/legacy/99CABBAC-C975-4A06-8D99-064C6871EE80/ Applications/AfterEffects/CS4/Win/ADBEAFETCS4_LS7.exe

Download both links and then run the .exe file to proceed with the installation. Activate the product using the serial number.

The key is not working 

If you have activated the key according to the guide but the code appears not to work, please check what type of error message you receive and depending on it follow the appropriate instructions:  

• My key is Duplicated / Already used
• My key is Invalid
• My key is region locked / can't be activated in my country
• My key activated a different product
• My key did not activate all of the content