Error 4005 when restoring IPad Pro

I have a 3 year old IPad Pro that suddenly went blank on me. When in charge the Apple logo flashes on for a couple of seconds every minute or so. I put it into recovery mode and connected it to my Mac to restore but this keeps failing with error 4005. The same thing has happened when connecting to a Windows PC. The latest operating system and ITunes are installed on both the Mac and PC. I can only get the IPad into recovery mode when it is connected to a charger or a Mac/PC. When it is standalone it appears to be completely dead. Any suggestions?