If the interior outlet turns red, it basically means something's blocking it from providing power. Here's what I've found:
The car needs to be on: It has to be in 'READY' or 'Utility' mode, not just 'Accessory'.
Charge port door must be closed: Makes sense, right?
Nothing can be plugged into the charge port: This includes your charging cable. The only exception is if you're using the external V2L (Vehicle-to-Load) feature.
Now, about the V2L. In my experience, it usually works as long as you've plugged something in, even if the car is off. However, if the car is on in 'READY' mode and you're not using Utility Mode, it'll automatically shut down after 90 minutes.
I'm wondering if there's a shorter timeout for the V2L when the car is off.
Another possibility is the minimum battery charge setting. You can set a level below which the V2L will automatically cut off to prevent you from getting stranded. The default is 20%, and you can't set it lower. Could that be the issue?