I manage to connect to the network and disconnect from it after sending the data, but if I'm in an area without reception, the device tries to connect and after a while, the device is unable to connect again and then when I return to an area with reception, I am unable to connect to the network and I receive the error messages I mentioned earlier.
I get from the lte_lc_connect() function error #-119 (-EINPROGRESS)
mqtt.m_modem_configure: Failed to establish LTE connection: -119