2015 International Prostar TCM not showing up in the line up

Hello my fellow Prostar owners.. unfortunately I am here I have exhausted all leads to fix this issue. Any advise is greatly appreciated. I owned 2015 international Prostar Cummins and with an automatic transmission. I have been fighting issue with electric fault on the dash every time the battery drains or if you let it sit for a week the Tcm would have to be programmed for the last 2 years money pit. Finally mid December when the tech hooks up the computer he was an able to see the Tcm . You can see the ecm and bcm but not tsm. He checked fuses all good. He thinks its the chassis harness, one of his other tech went through it didn't find anything. He suggested we need a new harness. 6 weeks to make it and $5400 for being not sure if its the problem.. any help or ideas. Thanks
PS.. 2021 we replaced the TCM with a new one.
2020 we replaced the harness that sits on the top of the transmission

 

truck is completely off the only thing running is refrigerator even that is turn down.
when it sits for week properly between 10V to 12 volt

 

That would be greatly appreciated