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Call forwarding not working — troubleshooting guide

Fix missed or incorrectly forwarded calls in SparkTG. Covers missing country codes, wrong trigger conditions, SIP registration failures, and DND restrictions.

5 min readLast updated 11 May, 2026By SparkTG Support Team

Call forwarding failures generally fall into two buckets: the forward was never triggered (routing logic issue), or it was triggered but the destination didn't answer (termination issue). This guide covers both.

Check the forwarding configuration

  1. 1

    Verify the destination number

    Dashboard → Numbers → your number → Forwarding Settings. Confirm the destination includes the country code (e.g., +91 for India). Missing the +91 prefix is the #1 cause of forward failures.

  2. 2

    Check forward trigger conditions

    Forwarding can be set to Always, On No Answer (after N seconds), On Busy, or On Unreachable. If set to On No Answer but the agent's SIP client is offline, the system treats it as Unreachable — a different condition. Set the correct trigger.

  3. 3

    Test with a different destination

    Temporarily change the forwarding destination to a personal mobile number and place a test call. If it now connects, the original destination number has an issue (switched off, DND, etc.).

SIP forwarding issues

  • SIP client must be registered (green dot in your softphone app). Unregistered SIP extensions will never receive forwarded calls.
  • Check SIP credentials haven't changed — go to Settings → SIP Accounts and verify the username/password match what's entered in your softphone.
  • Firewall blocking SIP? Ensure UDP port 5060 and RTP ports 10000–20000 are open. Many corporate networks block these.

Mobile number forwarding limitations

Forwarding to mobile numbers registered under DND (Do Not Disturb) with TRAI will fail silently. Use a landline or SIP extension as the forwarding destination for production setups.

Check Reports → Call Logs for the exact SIP response code on failed forwards. Code 486 = destination busy, 480 = temporarily unavailable, 404 = number not found.

Frequently asked questions

Why is my call forwarding working sometimes but not always?
Inconsistent forwarding is usually caused by the wrong trigger condition. If forwarding is set to 'On No Answer' but the agent's SIP client is offline, the system treats it as 'On Unreachable' — a different trigger. Set both conditions, or change to 'Always Forward' for testing.
Do I need to include +91 when setting a forwarding number in SparkTG?
Yes — always include the full country code with a + prefix. Use +91XXXXXXXXXX for Indian mobile numbers. Missing the country code is the single most common cause of call forwarding failures in SparkTG.
Why does my SIP extension not receive forwarded calls?
Your SIP client must be registered (showing a green status dot in your softphone). Unregistered extensions never receive calls. Also verify your SIP credentials under Settings → SIP Accounts match exactly what is entered in your softphone app.
Can I forward calls to a mobile number registered under DND?
No — forwarding to DND-registered mobile numbers will fail silently due to TRAI regulations. Use a landline number or a SIP extension as the forwarding destination for production setups. You can check DND status at the TRAI DND portal.
How do I find the exact error code for a failed forward in SparkTG?
Go to Reports → Call Logs → find the call → expand the record. Look for the SIP response code: 486 means the destination was busy, 480 means temporarily unavailable, 404 means the number was not found, and 503 means the downstream service was unavailable.

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