Can't select just the tcm to write to 2016 impala

I hope someone can help me with yet ANOTHER HP Tuners issue. I have a 2016 Impala at my shop. I have rebuilt the transmission and I'm having issues with the original TEHCM. I have purchased a USED TEHCM from another vehicle that had a good transmission. However, I need to program the used TEHCM to this car with the programming for this car. I plugged in the original TEHCM and downloaded the programming using HP Tuners. I then plugged the car harness back into the used TEHCM inside the trans. When I click "WRITE" in HP Tuners it pops up the dialog box to write the ECM, but gives me NO OPTIONS to skip the ECM and go straight to the TCM... USUALLY.. it gives me the option as to which computers I want to write to but it is NOT doing it this time... What am I doing wrong? WTF is the issue THIS TIME? How do I isolate writing directly to the TCM and do a WRITE ENTIRE? Anybody? Bueller? Bueller? It looks like these support forums get very little traffic.. I'm praying someone responds and lets me know their thoughts.

Do you have the ECM/TCM licensed? Or are you trying to write the TCM without licensing anything on the vehicle?

I purchased the license. I have heard "rumors" that you can somehow, some way, flash just the TCM without purchasing a license but I have never been able to do that.. I have ALWAYS had to purchase credits, license the vehicle, and then go from there.

Because HP Tuners is so unreliable, I am having a wrecker take the vehicle to the Chevrolet dealership this morning.. At least there I'm fairly certain they use something substantially more reliable than HPT (Hope & Prayer u can actuallyTune)...

If I remember correctly, used TECHMs have to have the VIN changed in order for them to be recognized by the car (ie the VINs throughout all the modules of the car MUST match). It's possible that the vehicle is seeing this discrepancy and denying you access to the TCM. I know USUALLY you can "Write Entire" to the module which changes the VIN reported by the module, but I'm not sure if this is a thing on the T43 TCM.

While I've never had to do a TECHM swap on a 6T70 and program it using HPT, I also see no reliability issues flashing calibrations to the TCM. Have done it on both Gen 1 and Gen 2 revision 6T70s and Gen 2 6T40/45 transmissions without issue. I hope you can get your issue fixed by GM.