J500fn flash err need help

DOWNLOAD FIRMWARE FROM OCTOPUS SUPPORT WHEN FLASH IT PUT PHONE IN DOWNLOAD WHEN TRY TO FLASH GIVE THE FOLLOWING MESSAG

Please put the phone into Download Mode and connect USB cable.
To put SM-J500FN into Download Mode, You have to perform the
following steps:
1. Reconnect the battery.
2. Press and hold "Volume-" + "Home" + "Power ON" keys.
3. When phone turns on, press "Volume+" key.
Found phone on
Firmware write started.
Writing Firmware Failed
Performed by 2.2.5 software version

WHEN PUT PHONE IN DOWNLOAD MODE SHOWS THERE .SECURE DOWNLOAD ENABLED