If the Multitech (ethernet-only) gateway completely stops connecting to the internet, not just our LoRa network server. Since this is an Ethernet-only gateway, the most likely failures are:
  1. Power failure (ie. PoE Injector failure, mains power loss - it could be switched off, power cable damage) 
  2. Internet connection failure (ie. Ethernet cable damage, Ethernet router/switch failure, Wi-Fi bridge failure - if you are using it)
  3. Temporary issue with the gateway

First check #1: look at the gateway LEDs, if they are turned on or flashing, power supply should be OK. 
If #1 is OK, then check #2. Best to unplug Ethernet cable from the gateway and connect to a laptop. If the laptop can connect with the internet via the Ethernet connection, then #2 is not likely the issue.
If #2 is OK, then unplug Ethernet cable between the gateway and PoE Injector (at whichever end it is easier to do) and plug it back after a minute to reboot the gateway. This should clear up #3 issue most of the time.

We had several customers experiencing PoE Injector failures in extreme cold or hot weather condition and resolving the issue by replacing the PoE Injector with the industrial-grade one. The bundled PoE Injectors are only meant for indoor use (ie. used in room temperature with low humidity). For outdoor installation (especially in extreme temperatures below 30°F or above 100°F), we always recommend appropriately rated PoE Injectors.