LS300 not responding form the internet in some countries

I’ m having trouble with LS300 modems as a 4G gateway. Everything is working fine in our labs, in France (provider=Orange), but when used in the United Arab Emirates at our client factory (provider=Etisalat), modem does not respond to requests coming from the internet (no response to ping and no access to the computer connected to the modem). Strange thing is, a computer connected to the modem is able to access the internet, so 4G connexion is ok.

Is LS300 supposed to work in the Emirates ?
(Band frequencies are the same in France and UAE, apparently )

Thanks !

Problem solved.
Our customer’s ISP in the Emirates is using SIM cards with private IPs natted to a public IP, so it explains why LS300 cannot be seen from the internet. It just cannot work in this configuration.