I am not sure how did you try reinstallation earlier. But the right way is to first uninstall the program by running the "Uninstall" application file as administrator. This file is kept in the installation directory at following location:
This would remove 2019R1 products completely. Now you can go for a reinstallation (as suggested, please run the installer with administrator rights). I would request you to please give it a try and lets see if it helps.