A very general answer....
Sorry, I can't be specific, but:
Some rigs have a switch on the dash that controls where the radio gets its power, the chassis battery or the house battery. If that switch is set to "house" and you turn off the house batteries (another switch, usually in the stairwell or next to the entry door) when you leave the rig, that may be cutting off power to the radio as you are experiencing.
Good Luck!
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