shortcuts automation has stopped working

I created a Shortcuts Automation "When battery level rises above 80%" "Turn off the Tapo Smart Plug". (it's a KP115). This worked well to limit charging level on my iPhone 13 mini (iOS 16.6). But recently it stopped working - the automation runs but says it cannot turn the device off. I installed the same automation on my wife's iPhone 13 mini and it worked as well, but now fails in the same way. I've force-restarted my phone but the problem persists. The Tapo app can see and control the KP115 as always. I'd welcome any ideas on what might be wrong and how to fix it.