Having only just bought Google Home Hub it's unlikely that factory resetting it is going to be top of your list of things to try, at least for now.
However, we had to do exactly that when our original setup of the device resulted in it speaking in a US accent to us and showing us US weather and news. A factory reset fixed the problem and it was soon serving up UK English.
The good news is that if you do have to perform a factory reset it's super-simple and yet impossible to achieve by mistake.
To reset Google Home Hub simply press and hold the volume-up and volume-down buttons together for 10 seconds. A warning will appear on screen that the device will be reset, and if you continue to hold the buttons that's exactly what will happen.
(Also see how to factory reset a standard Google Home.)