I have been using the router for over a month, contiously taking in and out the SIM card from the router. Everything was working fine.
Today, when I inserted the SIM, I did not have internet connection.
I have set back to factory all configurations as well as I have downloaded the logs to troubleshoot the issue. One of the most concerning messages is: "2016-01-01 00:03:04  4G: ERROR: Get sim card number failed (0)."
Still, the SIM works fine on my mobile phone.
It is worth mentioning the sticker used for the SIM is a bit broken and less sticky that it was.