Did you upload a 3D-printer firmware to the Mega2560? Which one, Marlin?
Did you configure Marlin for the LCD by activating REPRAP_DISCOUNT_SMART_CONTROLLER in Configuration.h?
If the firmware is well configured and uploaded, could the problem be due to bad contrast setting of the LCD? (In this case, you should still be able to hear the
"clicks" when you activate the rotary encoder.)
Did you configure Marlin for the LCD by activating REPRAP_DISCOUNT_SMART_CONTROLLER in Configuration.h?
If the firmware is well configured and uploaded, could the problem be due to bad contrast setting of the LCD? (In this case, you should still be able to hear the
"clicks" when you activate the rotary encoder.)