Hi,
I am using sdk_17 and nrf52810. I have build a bootloader from the examples folder(examples/dfu/secure_bootloader/pca10040e_S112_ble) for my device. After flashing, the device enters into dfu mode. When I select the required zip package from my phone for updating, it simple just gets disconnected. I am using the proper private and public keys for creating the files.