Atom,
Have you deleted the Alteryx files in "ProgramData" folder before reinstalling? If not, uninstall Alteryx Designer and then delete these files in "ProgramData". This folder is hidden and you will have to check "Hidden Items" to view this folder. Once completely uninstalled and the Alteryx Files are deleted, save the Alteryx download in File Explorer. Once the download is in File Explorer, right click the download file and select Run As Administrator.
Also, if you are using Run As User in the "System Settings of Alteryx" make sure the Service or User Account has access to all necessary File Paths. Screenshot below: