Phil, The first process you have to go through is Support. That button is on the Nest App, top left, press the 'Down' button and a drop down screen reveals your account name and a 'Support' button. That is where you can detail the fault and initiate the claim. Until you give them a chance to fix the item, you cannot progress the warranty claim.
Going straight to a warranty claim will not happen. The company has first to assess whether their product or services is at fault, or whether the user is at fault. Or go to a lawyer....but they will tell you the same. You have to jump through the hoops...first principles..
