Error when i try to flash my esp8266

hello . i need a help
when i try to flash my esp8266 with arduino mega i get this error
File "C:\Users\moi\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.0.2/tools/upload.py", line 66, in
esptool.main(cmdline)
File "C:/Users/moi/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.2/tools/esptool\esptool.py", line 3552, in main
esp.connect(args.before, args.connect_attempts)
File "C:/Users/moi/AppData/Local/Arduino15/packages/esp8266/hardware/esp8266/3.0.2/tools/esptool\esptool.py", line 529, in connect
raise FatalError('Failed to connect to %s: %s' % (self.CHIP_NAME, last_error))
esptool.FatalError: Failed to connect to ESP8266: Timed out waiting for packet header
esptool.FatalError: Failed to connect to ESP8266: Timed out waiting for packet header

please tell me where is the problem

To help you solve the problem you may want to post your code here so we can see what may be causing the errors.

I doubt that this a coding issue.

@medlab, what worries me is the use of the Mega; can you show the wiring that is used and describe the process that you followed.