This is a bootloader communication issue.
The baud rate in Marlins Configuration.h has nothing to do with this.
The baud rate is part of the bootloader. details can be found in boards.txt (part of arduino ide eg the line mega.menu.cpu.atmega2560.upload.speed=115200 )
possible causes
1) selected incorrect com port in Arduino IDE (so your not talking to the controller but something else)
2) selected incorrect Board in Arduino IDE (this sets incorrect parameters, including baudrate and upload protocol)
3) selected incorrect processor in Arduino IDE (no all boards have processor options)
4) bootloader on your board is not working or not present. (this can be due to being a wrong baudrate in bootloader). Time to setup a avrisp and write a new standard bootloader.
5) some boards require external power. ie cannot be powered up with just a usb cable. Eg RAMBo mini. (without this you see the com ports as it is powered by usb, but the processor is still powered off)
The baud rate in Marlins Configuration.h has nothing to do with this.
The baud rate is part of the bootloader. details can be found in boards.txt (part of arduino ide eg the line mega.menu.cpu.atmega2560.upload.speed=115200 )
possible causes
1) selected incorrect com port in Arduino IDE (so your not talking to the controller but something else)
2) selected incorrect Board in Arduino IDE (this sets incorrect parameters, including baudrate and upload protocol)
3) selected incorrect processor in Arduino IDE (no all boards have processor options)
4) bootloader on your board is not working or not present. (this can be due to being a wrong baudrate in bootloader). Time to setup a avrisp and write a new standard bootloader.
5) some boards require external power. ie cannot be powered up with just a usb cable. Eg RAMBo mini. (without this you see the com ports as it is powered by usb, but the processor is still powered off)