Unable to use file management software after upgrading to Android 11

Android 11 includes a new permission system to allow file access to apps.  Many apps have not yet adopted the new system.  To allow file permission manually for these apps go to Settings -> Apps ->  [File management app] -> Permissions and enable “Files and Media” access for the app. If you see permission options to "Allow while using this app" and "Allow all the time", select "Allow all the time".