I have bought a new package for PSE 2020 and cannot get past an Error code 50 ! It happened on the first installation with the DVD. I tried downloading the version 2020 from your website and got the same Error code? I then turned to CCleaner to wipe all past elements of PSE from my computer.
(I had installed the Trial version of PSE 2020 less than a week ago and it installed fine; which led me to buy it in DVD form from Amazon.com).
I used Task Manager in my Wiindows 10 Pro to try and find the so-called Adobed Installer to which this error code points to.
Are you installing using an Administrator account? If not, give that a try. Otherwise, I think you need to use the Adobe CC Cleaner which can be found under Solution 3 on this page. This cleaner tool also works for Elements. If you follow the instructions on the linked page for using the CC Cleaner, when you get to step 5, instead of choosing option 3, choose option 1 All. This should then enter a screen which lists Photoshop Elements 2020. (It may be identified as Photoshop Elements 18 which is the actual version number for Elements 2020). Once the cleaning process has completed, reboot your computer and start the installation again.