I guess you are using lookout runtime software. The "serial port" is disable in runtime.
You can add the following codes to lookout.ini in lookout folder.
[COM1]
LineType=0
ReceiveGap=20
AlarmPriority=1
DiagnosticFileEnable=1
DiagnosticFile=d:\log.txt
DiagnosticAllHex=1
DiagnosticTimeStamp=1
DiagnosticTimeStampDateFormat=73
If you use com2, just input [COM2]. The file path can be changed as you like.
Ryan Shi
National Instruments