Have you been able to open the program at all? Are you able to open the Welcome Sceen?
If you are on Windows, search for the file called PhotoshopElementsEditor.exe and double-click on it. (It should be at C:\Program Files\Adobe\Photoshop Elements 2021. Don't be confused by the Photoshop Elements 2021 folder icon which is not a regular yellow folder icon.) What result do you get?
If my suggestion doesn't work, you should try contacting Elements support. You can start a chat session by clicking on the blue Contact Us button under the Support menu at Adobe.com. Or you can contact Support by telephone using the numbers listed here: https://helpx.adobe.com/contact/phone.html.