@Avionic
Dear Avionic, I just finished testing again, and for some reason it worked now on both COM1 and COM2. I didn't change anything in FS'20, on the Duke's EFB and neither in the vPilot App. I remember clrearly that it didn't matter what COM was selected TX didn't light up in blue on neither COM1 & COM2.
vPilot done this on my end a few times, usually afer a vPilot update, I start to think I might have to restart the computer after an update, because that is the only thing I have done differently between today's test and last weekend's. There were numerous shut down and turn on cycles.
Anyways, I am glad it is working for now. Now I know it is not an issue with the Duke. Thank you for your ideas and time and effort trying to help. Same goes to @Black-Square .
Wish you all the best and great health and happyness. Cheers.