I had a strange situation, but knowing Microsoft is not hard to imagine. You want to setup an Office (2019 PRO in that case) but you cannot because of the preinstalled version (365) . I mean in online office account everything ok, installing on computer ok, but you have an error during installing and the licence key not working.
Open the Easy Fix tool and click Next. Click Yes. It may take a while to uninstall all of Office, so make sure your PC stays on. When the tool is done, click Next, and then close the tool. Restart your PC to completely uninstall Office. It’s magic !