When install old version product you may receive invalid license error, although you have input a valid serial number.
When old version products are no longer formally supported by our website, your cannot activate them through serial number anymore. However as a perpetual license, it is still valid to install the old version product. Instead of inputing a serial number, you need to select "Alternative way" to activate, and choose a License file to complete activation.
For how to get a license file for your license, refer to Where do I find a license for my software product? or How do I manage my licenses?.