Can not receive calls

Problem:

Customer is unable to receive inbound calls.

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Solution:

This is related to the IP Handset (IP Centrex), or the Gateway Device (IBL, PRI) ability to register to Thinktels network. There are a few possibilities:
1. Power Outages
2. Loss of Internet Connectivity
3. Router / Firewall security options are blocking VOIP traffic.
Note: Calls should still route to Auto Attendent and/or VM. Customer can also choose emergency routing options, i.e. route to cellular phones.