How to completely uninstall Microsoft Office
Leftovers from old versions often block activation of a new one.
Way 1: Windows settings
Apps, Installed apps, find Office, Uninstall. Remove trial copies too.
Way 2: the Microsoft tool
Download the Microsoft Support and Recovery Assistant’s uninstall tool. It removes what Settings leaves behind.
Way 3: check for old licences
In an administrator terminal, in the Office folder, run cscript ospp.vbs /dstatus. Remove old keys with /unpkey and the last five characters.
What to do next
Restart, then install the new version.
Will my documents stay?
Yes. Documents are not touched, but save Outlook data files and custom templates first.
Do I need my old key?
Keep it if you may reinstall that version.