When using an LTE device you can normally just use the "Auto" APN settings.
The configuration of the APN settings will be taken from the SIM as required. Some customers
have experienced an issue whereby the "Auto" settings do not work.
This occasionally can be routed in the device SIM being configured to support "Internet" but with IPv6
network as the default network - hence IPv4 connectivity does not work.
The answer to this is to go into "Manual" mode and enter the mobile providers APN Settings
manually specifying IPv4 as required. Here is a quick tutorial on how to do so on a LTE3301-PLUS, other models have fairly similar setup:
In case you might not know your internet service providers APN settings, there are many websites offering standard values listed for a plethora of providers, such as the following: https://www.4gapn.com/gb/en
(Please note that the link does not indicate any association between Zyxel & 4GAPN. The link just serves informative purposes, and Zyxel is not responsible nor affiliated with any of the content or their respective creators.)