I found the solution myself. The reason why the update did not work was that the batteries were half empty. After which I have used new batteries worked the update. I have to say that the logging function has become much better than in the beginning. Also the data can now be retrieved via Bluetooth or e-mail without removing the memory card is very good. What is still missing to improve the logging function is that the date and time display in the Mooshimer can be formatted in readable values. When testing, the app crashed two times and when reconnected, the Mooshimeter was in bootloader mode. A pressure on the reset button needed the device back to normal mode.