Does the drop-down in the application populate with the list of serial ports?
Are the COM ports the same? Your application reads the Serial Port at the very start of the application which means that changing the value in the drop-downs does nothing as the controls have already been read by that point.
You need to find a way to re-read the controls (e.g. in an initialise case of a state machine) if the user changes the value.
The image attached shows an image of MAX on the target machine.
I then tried to do a read in the input/output section and I get a read Operation Error.
VISA: (Hex 0xBFFF0015) Timeout expired before operation completed.
VISA: (Hex 0xBFFF003E) Could not perform operation because of I/O error
SAM_SHARP you are a legend. I changed the control to a constant. I'm glad it was just a programming bug on my behalf as installation was looking like it was going to be a pain, but all is good now.