Panasonic dmr es20 dvd recorder?

panasonic dmr es20 dvd recorder ?
Have a panasonic dmr es20 dvd recorder. I tape GH everyday. Its programed to tape automatically. Switched it out to tape a nighttime program but when I put GH back in it said this disc is not formulatedproperly.,do you want to format disc in management. If you say yes it says disc will erase all contents. Don’t want to erase, want to see the GH I’ve been taping. I may have pushed something accidently. Can you tell me how to fix this.