Delete the Media Cache and Media Cache files:
-pro/faq-how-to-clear-your-media-cache-in-30-seconds-in-premiere-pro-2020/m-p/11017257/thread-id/260446?page=1
If that doesn't work, try resetting the preferences:
-pro/faq-how-to-reset-trash-preferences-in-premiere-pro/td-p/8236158?page=1
If that doesn't work, try resetting the Workspaces:
Reset a workspace
Reset the current workspace to return to its original, saved layout of p
Open up premiere and created a new project. Next let's import our footage and background. You can drag the footage and background over to your project panel or you can go to "file" then "import" and do it that way.