Photoshop elements 15

Good day

In 2016 I bought on the adobe site this program. I then received adobe serial number that allowed me to install and register the software. Later having been uninstalled I needed it again. when I entered again the serial number an alert informed me that the serial number could not be validated. I was told that if I had an exchange code or a subscription email I could replace it.
But I have none of that, just the number sent by Adobe.
Can you help me ?

Thank you
jcl Ducourant