1. Check that the SIM card is installed correctly.
2. Check that the SIM card supports the same mobile frequencies that supports the smart clock.
3. Check the balance and the Internet of SIM card.
For a more detailed solution to the problem, you can contact support - https://elarihelp.freshdesk.com/en/support/tickets/new
The balance of voice call and Internet traffic on the SIM card. How to check?