All information about Ferduino Mega 2560 is here
In this point I can't guide you step by step. You have to search for solutions on Google since this is not a problem with Ferduino code.
Try install an example like this
using Arduino IDE.
If examples are working so try install ESP-link again.
Also you can try the latest version of ESP-link from here
If the magic error remains so try search a solution like this
in ESP8266 repository.
Otherwise you should buy another NodeMCU.
Moreover you should test the NodeMCU alone just connected to USB to make sure this is not a wiring error.