TL;DR If your Power is stuck in standby, reboot the gateway as below and contact Tesla and your installer. After a wait of almost 3 years (a whole long other story) we had two Powerwalls installed last September. In December I noticed that they were stuck on standby and not powering the house during evening peak rates like they were. I called Tesla energy support and they had me do a 'whole house reboot' that I described in another post. They claimed to have opened a ticket on it. A month later our Powerwalls were stuck again and this time support asked if my gateway panel had a hole labelled Reset you can access by just opening the front panel. No news on the ticket. Apparently the gateway uses a 'Neurio Meter' to monitor the electricity flow and it crashes sometimes. The first generation gateways did not have a reset button so you had to reboot them crudely with the whole house reboot or by carefully opening the gateway unplugging just the Neurio power supply like this guy does: *** be careful of the exposed high voltage wiring if you try this *** Mine has a reset hole, just stick something like a non-conductive plastic pen in straight in the hole and press for 10 seconds. You should some LEDs flash. I had to gently pry a fat wire out of the way with the pen. This got it working temporarily again. Tesla has since changed the gateways from gray to white, like a mini Powerwall, and I don't know where their reset it or if they need it. Fast forward another couple weeks, my Powerwalls are stuck again. I called Tesla Energy Support again and they said that the case from 3 months prior was being worked and that spare parts are being sent to my installer. It would have been nice if they told me. I called the installer Swell Energy and they say quite a few Neurio Meters have been going bad lately but unfortunately Tesla doesn't let them stock the part, each has to be ordered in response to a specific failure and it takes a month or two to get the part from Tesla - which sadly sounds like too many of the car repair horror stories.
OK my Powerwalls are back online. Interestingly my Neurio meter had not failed. The initial installers were good electricians but not too educated about Powerwall data links. They crawled through my very small crawlspace to pull a CAN data link wire from my Gateway to the subpanel next to my Solar Inverter and Powerwalls. They could have pulled another wire at that time but instead used a wireless Zigbee connection for the other data link. They sealed the Zigbee antenna inside the steel solar subpanel which blocked most of the signal. When the new guys came out the only part from the replacement Neurio Meter kit was the mount that allowed them to poke the Zigbee antenna out a punchout. Signal strength is great now and Powerwalls have worked well since. The logic that runs them doesn't work without data being reported from the solar feed.