If the 3G/4G/LTE connection is not working on the router, you may try the following steps to troubleshoot.
You can find the USB dongles supported by the router from Application >> Modem Support List on the router's user interface.
Note that Vigor Router provides two access modes, PPP and DHCP. The selection affects how will the router exchange data with the dongle, and the wrong settings may cause the connection to fail. Check the Support List to find the right one to use, or just try the other one if the current setting is not working.
The latest firmware includes improvements and fixes to known issues. If the router's firmware is not the latest version, upgrade the firmware and try again.
Make sure you are using a valid SIM card, not expired, data not used up yet.
Check if you have entered the right PIN code. Leave the PIN code field blank if the SIM card does not have one, which is also quite common.
Confirm the configuration in WAN >> Internet Access again. Make sure have entered the APN, username, and password that your ISP provided.
If none of the above solve the issue, please provide the following information to our Technical Support for further analysis.