I saw the prompt to update the firmware and initiated the update cycle. The result was that six of eleven cameras went offline. The error code was unable to contact network / check WiFi connection. The WiFi is, of course, just fine and not the problem. The cameras could not be turned off from the app and unplugging / plugging did not help.
I deleted one camera and did a new setup. This fixed the issue. However, removing the five remaining cameras from their various perches and doing new setusps will be very inconvenient.
Is there an easier workaround that will address this problem?