@leftturnclyde 

Can you turn on the hotspot on your phone and use the tablet to do the configuration again?  You may also try to enable a 2.4GHz guest WiFi for testing. 

Note: Please restore the device to factory settings before each reconfiguration.

How to reset Tapo C500: Use a pin to press and hold down the Reset button for 5s, led will start blinking red quickly, then turn to blinking red and green (ready for setup).

What's the model of your starlink router? Can you provide a screenshot of the error?

Please make sure your Tapo APP is the latest version.

  @leftturnclyde 

Please verify whether your phone is connected to the 2.4GHz WiFi "Ltc" during the pairing process: When the App displays Pairing to your smart device, keep Tapo running in the background and go to WiFi settings to check the connected wifi.

If your phone connects to 5GHz WiFi, it may cause pairing failure.

There is a simple way to verify if the router setting is causing the issue, factory reset and reconfigure the router. If this is acceptable to you, you can have a try. 

  @leftturnclyde 

Restoring the factory settings of the router is the quickest way to determine whether it is some special settings on the router that you do not know or are not aware of that cause the device to fail to connect. This method is not a mandatory and recommended method, but an optional suggestion. Some users with simple network topology may choose this method to solve the problem quickly.

For your case, we would like to escalate it to the support engineers, and they will help follow it up, if you are willing to do further analysis, please check your inbox later and respond.