In both cases, it’s a condition of your insurance policy that the black box remains plugged in at all times. If the device is unplugged or damaged, it will stop transmitting data to the insurer, alerting it immediately that the black box isn’t working.
If you unplug the device or interfere with it in any other way, your insurer may revoke any discount on your premiums that you have earned through the black box - you can't trick a black box. They may also cancel your policy and could refuse to pay out on claims made about the period in which the device was unplugged. You will be notified if your premiums are adjusted or your policy is cancelled due to your black box not being on. Having a car insurance policy cancelled may make it more difficult or expensive for you to secure insurance in the future.
If you or a mechanic must unplug the device, or if it’s unplugged accidentally, insurers require you to plug it back in immediately. This may require a visit from a professional. If you don't know how to plug your black box back in and it's not a self-fit model, you shouldn't attempt to do so on your own, as you may damage your vehicle. Instead, contact your insurer as soon as possible.
If your black box stops working while it's still plugged in, you should contact your insurer as soon as possible about having the device repaired or having a new one fitted. Your insurer may also contact you if they notice your device is no longer transmitting data on the chance that you’re not aware it’s malfunctioning or unplugged.