ramps 1.4

i have a problem with ramps 1.4 .. when i connect it with arduino mega 2560 then port error occurs . arduino shows port hidden .ponterface ,repitier host shows port connection error..
ponterface shows this error :
[ERROR] Could not connect to COM4 at baudrate 250000:
Serial error: could not open port COM4: [Error 2] The system cannot find the file specified.
please help me

... check for shortcuts - especially the pins above the USB-housing on the Arduino Mega ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

i just merged ramps on arduino .. they are connected .. but when i upload firmware ..arduino shows port as hidden icon