Hi!
I also have trouble with mega 2560 and firmata. Using the servo and analog pin modes, it works but the digital pins are dead.
For example I tried to follow this great tutorial: firmata-arduino-and-vvvv-an-introduction. Following the indications the servo and the potmeter examples works fine, but the button example with digital input is not working.
I changed the FirmataEncode and Firmatadecode pin numbers in Inspektor to 16 analog and 54 digital input count, Pin Modes and Input box to 70. I saved and restarted the patch. When I push the button on breadboard the pin nr. 2 (or any other) digital input value is not changing like in the video… I don`t know what is the problem.