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Troubleshooting

Troubleshooting

This section covers common issues encountered with NexusUC and VoIP systems in general. Use this guide to diagnose and resolve problems before contacting support.

No Audio on Calls

Symptoms: The call connects but neither party can hear anything — complete silence in both directions.

Common Causes and Fixes:

  1. NAT/Firewall blocking RTP traffic

    • Ensure your firewall allows UDP traffic on the RTP port range (typically 16384–32768)
    • If using a remote PBX, verify that the SIP proxy port is open and forwarded correctly

  2. Codec mismatch

    • Ensure the phone and PBX are using the same audio codecs (e.g., G.711a, G.711u, G.722)
    • Check under Accounts → Extensions → Selected Extension for codec settings

  3. SIP ALG enabled on router

    • SIP ALG (Application Layer Gateway) on consumer routers frequently causes audio issues
    • Disable SIP ALG in your router's settings — this resolves the majority of no-audio issues

  4. Incorrect network configuration

    • For on-premise PBXs, ensure the device and PBX are on the same network or that proper routing exists between subnets

One-Way Audio

Symptoms: One party can hear the other, but audio only flows in one direction.

Common Causes and Fixes:

  1. SIP ALG interference

    • Same as above — disable SIP ALG on your router as a first step

  2. NAT traversal issue

    • If the PBX is behind NAT, ensure the external IP is correctly configured in the PBX SIP settings
    • For phones behind NAT, enable STUN or configure the phone's NAT settings

  3. Asymmetric firewall rules

    • Verify that both inbound and outbound UDP traffic is allowed on the SIP and RTP ports
    • Some firewalls allow outbound but block return traffic

  4. Phone behind double NAT

    • If the phone is behind two layers of NAT (e.g., ISP router + office router), this commonly causes one-way audio
    • Place the office router in bridge mode or configure port forwarding on both layers

Registration Failed

Symptoms: The phone or softphone shows "Registration Failed", "403 Forbidden", or "401 Unauthorized."

Common Causes and Fixes:

  1. Incorrect credentials

    • Verify the extension number and password match what's configured in Accounts → Extensions
    • Passwords are case-sensitive — re-enter them carefully

  2. Wrong SIP server address or port

    • For on-premise: Use the PBX local IP with DNS SRV transport and port 0
    • For remote/VPS: Use the domain with TCP/UDP transport and the Proxy Port from the portal
    • See SIP Endpoint Registration Options

  3. IP blocked by firewall / IPS

    • NexusUC's Intrusion Prevention System may have blocked the device's IP after too many failed registration attempts
    • Check the firewall whitelist and unblock the IP if necessary

  4. Extension not enabled

    • Ensure the extension is enabled under Accounts → Extensions → Selected Extension

Call Drops / Calls Disconnecting

Symptoms: Calls connect but drop after a specific time (often 30 seconds or 2 minutes), or randomly disconnect.

Common Causes and Fixes:

  1. SIP session timer expiry

    • If calls drop at exactly 30 seconds, the SIP INVITE is likely not receiving a proper response — check firewall rules for SIP traffic

  2. NAT keep-alive not configured

    • Phones behind NAT may lose their registration mid-call
    • Enable NAT keep-alive on the phone (usually a 30-second interval) to maintain the connection

  3. Unstable internet connection

    • Packet loss or high latency on the internet connection causes call drops
    • Run a network quality test — VoIP requires less than 1% packet loss and under 150ms latency

  4. SIP ALG interference

    • Again, disabling SIP ALG resolves many intermittent call drop issues

Poor Call Quality / Choppy Audio

Symptoms: Audio is garbled, choppy, robotic, or has echo.

Common Causes and Fixes:

  1. Insufficient bandwidth

    • Each concurrent call requires approximately 100 Kbps of dedicated bandwidth (using G.711)
    • Ensure your internet connection has sufficient upload and download capacity for your call volume

  2. Network congestion / no QoS

    • Enable QoS (Quality of Service) on your router to prioritize VoIP traffic over other data
    • Place phones on a dedicated VLAN if possible

  3. Jitter and packet loss

    • Use a VoIP quality test tool to measure jitter (should be below 30ms) and packet loss (should be below 1%)
    • Switch to a wired connection if phones are on Wi-Fi

  4. Echo issues

    • Echo is typically caused by the phone hardware — update the phone's firmware to the latest version
    • Reduce the speaker volume on speakerphones

Voicemail Not Working

Symptoms: Calls don't go to voicemail, voicemail greeting doesn't play, or voicemails aren't delivered to email.

Common Causes and Fixes:

  1. Voicemail not enabled

    • Check under Applications → Voicemail that the inbox is set to Enabled
    • Verify the extension has voicemail configured under Accounts → Extensions

  2. Greeting not assigned

    • If no greeting plays, ensure a greeting file is uploaded and selected under the Greetings tool for that voicemail inbox

  3. Email delivery failing

    • Verify the Mail To email address is correct
    • Check that Audio File Attachment is enabled
    • Confirm the PBX mail server settings are configured correctly (SMTP settings)

  4. Voicemail password issue

    • If users can't access voicemail by dialing *97, verify the voicemail password matches what's configured

Phones Not Provisioning

Symptoms: New phones don't auto-configure, or provisioning changes don't apply after saving.

Common Causes and Fixes:

  1. MAC address not entered correctly

    • Verify the 12-digit MAC address under Accounts → Devices matches the label on the phone exactly

  2. Provisioning not triggered

    • After making changes, click the Provision button on the device page
    • If changes still don't apply, go to Status → Registrations, tick the device, and click Provision followed by Unregister to force a reboot

  3. RPS not configured (Yealink)

    • For Yealink devices, ensure the domain has been added to the RPS server under Applications → Yealink RPS
    • The device must show a '–' icon (not '+') indicating it's been added to RPS

  4. Factory reset required

    • If all else fails, perform a factory reset on the phone and allow 10–15 minutes for it to re-provision

Call Recording Not Working

Symptoms: Calls are not being recorded, or recordings are not available in CDR.

Common Causes and Fixes:

  1. Recording not enabled for the extension or queue

    • Check that call recording is enabled under:
      • Accounts → Extensions → Selected Extension for individual extensions
      • Applications → Call Centers → Selected Queue for queue calls

  2. Storage space full

    • Call recordings consume disk space — verify the PBX has sufficient free storage
    • Clean up old recordings periodically

  3. Recordings not appearing in CDR

    • Navigate to Applications → Call Detail Records and check the Recording column
    • You can also check Applications → Call Recordings for a dedicated view

Fax Not Sending or Receiving

Symptoms: Outbound faxes fail, inbound faxes aren't received, or fax notifications don't arrive by email.

Common Causes and Fixes:

  1. Fax codec issue

    • Fax requires T.38 or G.711 codec — ensure the SIP trunk supports fax passthrough
    • Compressed codecs (G.729, Opus) will cause fax failures

  2. Email notification not configured

    • Verify the recipient email address under the fax server settings
    • Ensure Send as Attachment is enabled

  3. Fax destination number incorrect

    • The destination number must be configured under the fax server settings and match the fax server extension

When to Contact Support

If you've tried the relevant troubleshooting steps above and the issue persists, contact Localcom support through the Partner Portal.

Include This Information in Your Support Request

Providing these details upfront will help resolve your issue faster:

  • PBX domain name
  • Extension number(s) affected
  • Date and time the issue occurred
  • Call ID (if available from CDR)
  • Brief description of the problem and what you've already tried
  • Screenshots of any error messages