Hello Marco,
Please kindly check your motherboard first,
If your motherboard is V4.1,please download the following firmware:
"Firmware For A20(ONLY for GT2560 V4.1 series motherboard, Selectable 3Dtouch function)"
If your motherboard is V4.0, please download the following firmware:
"A20_G05(CH340 Support 3Dtouch)"
The firmware link as following
https://www.geeetech.com/download.html?download_id=32