VoIP: What to Do When Your Phone Shows 'No Service' or Won't Register

If your VoIP business phone shows "No Service," "Unregistered," or won't make or receive calls, here's what to check. Step 1: Check internet connectivity VoIP phones need internet to work. On a computer on the same network, confirm you have internet access. If there's no internet, fix that first — your phones will come back online automatically. Step 2: Restart the phone Unplug the phone from power (or the Ethernet cable if powered over PoE) for 30 seconds, then reconnect. The phone will re-register with the phone system server on startup. Step 3: Restart the router If multiple phones are showing no service, restart the router/firewall. This often clears stale network connections that prevent SIP registration. Step 4: Check SIP ALG (if problems persist after restarts) SIP ALG is a feature on many routers that's meant to help VoIP but often breaks it instead. If you've had recurring registration issues, this is a likely culprit. Contact us and we can check your router settings and disable SIP ALG if needed. Step 5: Check the phone's network connection Make sure the Ethernet cable is firmly seated in both the phone and the wall/switch port. Try a different cable or a different port on the network switch. Step 6: Check if your phone system provider has an outage Log into your phone system's admin portal or check their status page. Some providers have a service status page — check there for any known outages. Step 7: Contact us If none of the above resolves it, we'll need to check: - The phone's SIP credentials (username, password, SIP server address) to confirm they're still valid - Whether the provider has de-provisioned the account - Router firewall rules that may be blocking SIP traffic on port 5060