You don't mention if you tried this, but if they're not flashing the first step is to force your phone onto your 2.4GHz SSID to see if it can find the switches. If it does, make sure remote access is enabled - then your phone will probably find the switches when you go back to your 5GHz SSID. If not, try rebooting your router. The problem must be network/app connectivity as it's unlikely all of your devices would fail at the same time.

@smithhn 

 

Hello, how many smart plugs and bulbs do you have? And what are their model number? 

 

Try to reboot the smart home devices; and you can delete the App and reinstall it. 

 

You can reboot the main router to give it a go as well.

 

Still the same, you can take one or two of them to reset and reconfigure. 

 

May it help. 

@smithhn 

 

Hello, thanks for your valued reply, glad to hear that you figured it out finally. 

 

It helps a lot.

 

Good day. 

 

@BigNickUK Don't reset anything, it's unnecessary trouble and can mess things up further. 

If the tp link devices are flashing amber or otherwise indicating they're not connected to wifi, the suggestion here is to reboot/restart your router first.  Wait a minute and then restart (not reset!) any of the tp link devices that are still indicating they're not connected to your wifi.

Once the tp link devices are connected to your wifi (double check in your router status), if they're still showing not connected in your app you've got some other problem.  Try turning off wifi on your phone to see if they're available over the data network.  If yes, try reconnecting your phone to your 2.4GHz ssid to see if it can find them.  If no, there's a router or network issue you'll need to sort (how depends on your router or provider).