It is recommended to have the Internet connection mode set to "4G LTE Broadband Connection".
Access the router configuration tool then click Router Settings (on the left).
For assistance with accessing the router configuration page, refer to Accessing the Router Configuration.
From the Advanced tab, select Broadband Settings then select Always use 4G LTE Broadband connection (from the Internet Connection Mode dropdown under Broadband Settings) then click Apply.
Ensure the Domain Name Server (DNS) Address is set to Get Automatically from ISP.