Photons do not reconnect to wifi when the router is power cycled

Three photons all within feet of the router with excellent signal level (-58). I had to change the power source for the router and was surprised that not a single one of the photons connected to the router 10 minutes after power on until I pushed reset on each one. Why is that? What factors contribute to that behavior?

That should not occur. What color was the status LED before you reset the devices? Was it blinking green (trying to connect to Wi-Fi), fast blinking green (DHCP), blinking cyan (connecting to the cloud), or fast blinking cyan (authenticating), or something else?

And what version of Device OS is running on them, which SYSTEM_MODE, and is SYSTEM_THREAD enabled?

Hi, thank you. The person in charge of iot also agrees it should not occur and is equally puzzled by it.
They all were blinking green. After reset they quickly moved to fast green and then connection. I will see if I can find the other information you requested. If there was one parameter which could accidentally be disabled that would cause this, what would it be? Or are there several?

Update. Googling and reading about system mode and thread. Beginning to see the light…