Interestingly I've been having the same problem with the new SD card. When I contacted Renault, they've sent me a second card, asked for the engraved serial and production codes on the back of it, and when that failed to work they got me to do a Factory Reset. Doing that has given me about 4 days of usable maps before it started to do the no maps found, Powering Off loop. I've gone back to them today to report it and waiting to hear back. Have resorted to loading the old card back in. Just for reference, the reason the card appears blank when viewing them in Windows is due to the file system the cards use. It's a Linux file system called ext which Windows doesn't understand so it just appears blank.