Hello,
From your description it seems that SIM card which you are using in the router simply does not have "Public IP address". I.e.:
- Router can see, that it receives "100.76.x.x" IP address from mobile operator
- From "outside" (internet) same IP address is visible as "109.x.x.x"
- Since these two IP addresses does not match, this indicates that SIM card receives "Private IP address" from mobile operator. If needed, we have a wiki article where Public and Private IP address aspects are explained in more detail. You can find article here: https://wiki.teltonika.lt/view/Private_and_Public_IP_Addresses
Solution in this case is simple: you would need to contact your SIM card provider and ask for "Public IP service" to be enabled on this particular SIM card.
Once you do that, take note that there is easier way to check if router have received Public IP from operator:
- Navigate to router's "Status -> Network -> WAN" menu and check router's "IP address"
- Try to access internet from any device, which is connected to this router, and visit any web page, which would show router's IP address, which is visible from "outside", e.g. https://ping.eu/
- Compare both IP addresses. If they match - you have Public IP address.