Hi I m sorry to hear that. This is usually caused by an electronic component failure a memory IC.
I woudl really just buy a new unit because between shipping, time lost and parts & labor it will be almost as much as a new one. I wish i had better news for you I really do, But that s what even I would do at this point given what happened.
If there is anything else I can help with please let me know?
I hope that helps, Have a great weekend and best of luck with your new GPS!
please don't forget to rate kindly so I can close this for us, no cost to rate.