Can't read an analog signal with Mega2560

[Maass]

Hi,

after a few trials the arduino (or Labview ) is not able to read an analog signal

wich comes from a simple potentiometer.

The RX-LED on the Mega is blinking... that's all.

I use the NI full development 2017 version and the LIFA-Base is correctly programmed to the Arduino Mega 2560 (Elegoo Mega 2560 R3)

Measurement & Automation Explorer says: 

Error opening resource:
ASRL4::INSTR

VISA: (Hex 0xBFFF0072) Die Ressource ist zwar gültig, aber VISA kann im Moment nicht darauf zugreifen.

Has somebody of this community a good advice for me...?

Thanks a lot for Help !