Xiaomi Mi Max lock with screen with picture of phone with usb cable and "pcsuite.mi.com" url, regular reboot, no pcsuite connect
Try booting with both volume up and down pressed, and only then connect to the pc, if the PC recognizes it as Qualcomm 9008 (COMsomenumber) you are set, open MiFlash and flash the latest ROM
Hope this helps :)