Serial No.# Invalid?

Hi, I bought a copy of Adobe Premiere elements 2021 on Amazon and installed it on my PC and installation went fine. but while using it I was having performance issues (glitching and freezing/running slowly, lagging) that I realized were because my PC could'nt handle the heavy load. So I bought a new Mac and downloaded  Premiere elements 2021but I can't activate it as the system says my serial No.# is invalid? anyone knowwhat will solve my problem? I've tried support page on the program and it has me chasing my tail. any help appreciated. thanks