It's the Dymo LabelWriter 400 isn't it?
Did you try the latest DYMO LabelWriter Software v126.96.36.199 from click here.
Couldn't find anything that relates to your problem or model - see click here (& click on Error messages). Not sure any of these will help click here.
May be best to contact their Tech support on 020 7341 55 29 - Monday to Friday: 9am-5pm (from click here), or use the Tech support email form click here. Good luck, G