Sure, take your pick or use both:

- To the shop: You said you could fix this. It appears now you are unable to fix this, so you can't live up to your commitment. Please direct me to someone who can, or sub the repair out to someone who can. Is this another shop? . . . or a dealer? . . . or something else? . . . doesn't matter, it needs to be fixed.

- To the insurance: You committed to fix this in return for me paying for a policy with you. It appears now you have decided this is optional. I need a clear written explanation as to why you believe this is optional so that I may consider my next steps to resolution.

You're not going to strong-arm them into anything without a lawyer, but you can certainly require that they provide you a written reason for denying their part of the deal. Without that, you (and we) don't have a way to proceed to any next steps, and they know that. I have heard of insurance companies settling for a small amount when it is uneconomical to repair a certain thing, like [that taillight is still cracked but functional, and it is impossible to find a replacement, so we would like to compensate you for NOT repairing it]. Maybe that'* also an option that they don't want you to know about.

Right now, my picture of this is:

1. Car was good
2. DEER!
3. Some repairs happened
4. For some reason they won't or can't proceed with the last part of the repair

The reason I was asking about them totaling it is that if they can't fix the vehicle, totaling is the next logical step. If it were me, I think I'd be happy to say something at this stage like, "Hmmm, sounds like you can't repair it. Go ahead and total it then and I'll go find another one." then I'd beat them into a fair price, and then later, once that'* settled, I'd call them quite separately, like a day later, and ask them "How much for me to buy it back?". They usually work this as a deduction of the total-loss settlement.

First, before all of that, I'd need to know more about the specifics of the refusal. They can't just say "no" without some explanation.

Here are some pix the body shop sent me of their tests and I also have pinout diagrams of the active shutter plugs they gave me as well. Based on these pictures, does it shine any light on what I may be able to do to remedy this issue I’m having? Like can I run a solo wire to a switched power source and tap into the plug that way?

That gets iffy on the newer cars, besides, if you run a wire around what it can see, you'll probably get a light for the light being out.

I’m not sure I follow what you mean by getting a light for the light being out, could you elaborate? I was just thinking that if the plug is getting 0.0 volts, maybe I could just tap into another switched power wire that turns on with the ignition and be able to get power to the shutters while the truck is running

Here are the pinouts for both ends of the plugs. One being off the shutter and the other being of the trucks wiring harness, if it helps any…

I meant, in the process of bypassing the headlight for the code, if the BCM sees the headlight circuit not responding the way it would with everything connected properly, it might illuminate a light on the dash to warn you of this. I don't know if the 2016 Escalade warns of such things, but I think it does.

As for the shutters, I don't think it is an analog item. I think it needs the BCM to tell it how far open or closed to be.