D:\Arduino\libraries\RobotIRremote\src\IRremoteTools.cpp:5:16: error: 'TKD2' was not declared in this scope
int RECV_PIN = TKD2; // the pin the IR receiver is connected to
^
Multiple libraries were found for "IRremote.h"
Used: D:\Arduino\libraries\RobotIRremote
Not used: C:\Users\Marietherese\Documents\Arduino\libraries\Arduino-IRremote-master
exit status 1
Error compiling for board Arduino/Genuino Mega or Mega 2560.
The Arduino IDE is confused because there are two different libraries that have files named IRremote.h and it's incorrectly chosen to use the RobotIRremote library included with the Arduino IDE.
Rename the folder:
C:\Users\Marietherese\Documents\Arduino\libraries\Arduino-IRremote-master
To:
C:\Users\Marietherese\Documents\Arduino\libraries\IRremote
that should cause the Arduino IDE to use the correct library because the folder name will then match the file name.