Google Can't Reach SmartThings

My Google Assistant on my phone has been refusing to turn on and off the 2 devices I have on smart plugs: "Can’t reach SmartThings."

I found an article about the Google Home doing the same thing. Fortunately, the advice there worked: go into Assistant’s settings → Devices → Add Devices. Upon clicking on the SmartThings entry that was already there, it gave me the option to re-link. Once I authorized access, I could again ask Google to control those devices.