Looks like I bricked mine 
Device path .: /dev/ttyACM0
Firmware file: deCONZ_ConBeeII_0x26780700.bin.GCF
Timeout .....: 60
Are the above values correct?
Enter Y to proceed, any other entry to exit: Y
Flashing...
GCFFlasher V3_17 (c) dresden elektronik ingenieurtechnik gmbh
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
deCONZ firmware version 26580700
R21B18 Bootloader
Vers: 2.07
build: Jun 17 2019
flashing 163230 bytes: |=====error: timeout flashing firmware after 3004 ms
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
R21B18 Bootloader
Vers: 2.07
build: Jun 17 2019
flashing 163230 bytes: |===========error: timeout flashing firmware after 3003 ms
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
R21B18 Bootloader
flashing 163230 bytes: |=error: timeout flashing firmware after 3001 ms
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
R21B18 Bootloader
Vers: 2.07
build: Jun 17 2019
flashing 163230 bytes: |=error: timeout flashing firmware after 3002 ms
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
R21B18 Bootloader
Vers: 2.07
build: Jun 17 2019
flashing 163230 bytes: |=error: timeout flashing firmware after 3002 ms
Reboot device /dev/serial/by-id/usb-dresden_elektronik_ingenieurtechnik_GmbH_ConBee_II_DE2475236-if00 (ConBee II)
retry, failed
2408: Error: uart reset failed, check retry
Flashing Error! Please re-run this script...
# docker run -it --rm --entrypoint "/firmware-update.sh" --privileged --cap-add=ALL -v /dev:/dev -v /lib/modules:/lib/modules -v /sys:/sys deconzcommunity/deconz
Now my laptop don’t even see the ConBee when plugged… Is there a solution?
Edit: It’s back after unplugging it for a while!! Magic.