My relative who works in Adobe ordered an Acrobat Pro 2020 for me. I received an email form adobe with the Redemption Code. I was then able to go to www.adobe.com/go/getserial and obtain a serial number. I then download Acrobat Pro for my Mac and attempted to install it. When I enter the serial number, I get a message "Invalud Serial Number" This is not a valid serial number. Please re-enter your serial number. I then went into my My Products page in my account. I was able to successfully register this, but the platform says Windows even though I'm using a Mac and at no point was i asked to choose between Windows and Mac.
They probably got for you the wrong product, then. The perpetual license version is platform-specific, unlike the subscription version. If you bought a license for Windows you can't use it on a Mac, and vice versa.
You should contact Adobe directly to help you switch platforms for your license. We can't help you with that.