You encounter error 619 when the modem can't reach the destination servers. This is usually caused by a firewall installed on your computer, or when the servers are actually not accessible. You can either try again or add the software to the Exclusion list.
For error 628 has multiple causes, but in order to fix it, you need to do the following:
call your Internet provider and make sure that the SIM card used in the modem is configured for Internet.
check your balance and add more credit if necessary.
move to another room with clear reception then try to connect again.