Update your system software to the latest version.
If your external storage drive cannot be recognized, unplug the connected USB cable and plug it back in.
If you are using a USB hub, remove it and connect the USB storage device directly to your PlayStation®5 console.
Your external storage drive needs to be formatted if you want to use it as extended storage for the first time. To format as extended storage, go to Settings > Storage > Extended Storage.
If you cannot transfer your data all at once, try transferring content individually.
Please check whether your game data can be installed on extended storage by visiting the PS5 extended storage guide below.
There may be an issue with your external storage drive. Please try using another storage device.