Please check your public IP address that runs your VoIP lines - to do this - connect to that router on your PC and type into a browser search field 'What is my IP address?'
This will display your public IP address - please advise us whether this is Static or Dynamic? You may need to contact your Internet Service Provider (ISP) to find out.
If the IP address is static then it may be that your phone will need to be re-configured for a Static IP address as normally Dynamic IP addresses are used and so phones will be configured for these types of IP addresses.
Please provide us with your VoIP IP address which can be accessed via your phone - please click here to see how.
Please also provide us with your Public IP address so that we can check neither of these are blocked.
Please also check if your router which runs your VoIP service is activated for DHCP?
Has the SIP ALG setting been disabled on your router?
Have you checked the port settings on your phone? It may be that these need to be changed, please click here to see how.
Is your firewall blocking your VoIP line?
Please provide the answers to the above questions to our Support Helpdesk so that we can advise further.