@Paul_Van_Dyke That is frustrating! I do not use the KX3 or Ham Radio Deluxe, but I do not want your concerns to go unanswered.
It sounds like the Digirig and Elecraft KX3 work together when connected with K0TX’s cable. Am I right? That’s good!
It also sounds like you are using a Virtual Serial Cable to connect something to HRD, Ham Radio Deluxe, probably for CAT control. Am I right?
Denis K0TX has an explanation of the connections here. Does this make the situation more clear? The posting mentions that the cable must be ordered as a null modem cable.
There is also a guide Troubleshooting Digital Modes – digirig.
73 Constrainted