Thank you all for your suggestions!
I believe I have configured the phone and the router as suggested but I am still having issues with internet access. I have NOT done the DMZ suggestion because I was not sure what IP address to use for the DMZ Host IP field.

The phone is called ‘Blue Honor 8’. This is repeater mode

Ping tests.
PC → X750 → phone - tethered

X750 → phone-tethered

Let me know if you see something I have missed or if you can think of any other tests. Also, if you can confirm what DMZ IP address I should use I will do that test as well.
Thanks again.