A few days ago my Model X from March 2017 with EAP lost its Autopilot features. It never seems to become available anymore as I'm driving. Navigate on Autopilot doesn't show when I set navigation. The steering wheel icon that shows next to the speedometer in the center display never comes up anymore. When I try to engage Autopilot or cruise control from the steering wheel stalk, it says "Cruise control unavailable". A few days ago everything was working fine. Any ideas? I made a service center appointment but it is a week away.
Most likely, you need to install another firmware update over-the-air and you don't need to spend time driving your car to a Service Center. Please give your Service Center a call and reference what I said above so they can push another firmware to your car over-the-air.
Try doing a reboot of the processors. You may even want to go through a power-down/power-up cycle. And see if this corrects the problem. Getting an OTA software update might also fix the issue. Our AP 2.0 2017 S 100D periodically loses the side cameras, which limits some features like NOAP or lane change - but haven't seen a complete loss of all AP features like TACC in either of our Tesla vehicles.
Glad power off worked for you, but as this could recur until/unless you get an update to prevent it, see this: Cruise control, auto headlights, autopilot not working