softwareupdate --fetch-full-installer --full-installer-version 10.15.7 Use code with caution.
You can try opening the official Mac App Store link in a browser. However, on newer macOS versions, this link may redirect to System Settings. download macos catalina 10.15.7 full installer
(usually labeled "Install macOS Catalina") from the startup manager. on newer macOS versions
Click the Get button. This will likely open the "Software Update" pane in System Preferences. download macos catalina 10.15.7 full installer
When you see "Done." in Terminal, your bootable installer is ready.
Run the installer again.