Hey there, let's get this sorted out! The key thing to understand right off the bat: SIP registration is NOT automatic with Twilio. You have to manually set up your Zoiper softphone to register with your Twilio SIP Domain—Twilio won't do this for you in the background. Here's how to fix your issue step by step:

1. Double-Check Your Twilio SIP Domain Configuration #

First, confirm the basics are set up correctly in your Twilio console:

• Make sure your SIP Domain has Registration enabled (you mentioned you did this, but it never hurts to verify in the SIP Domain's "Registration" tab)
• Ensure the SIP Credential you created is linked to the SIP Domain's Credential List (you can check this under the "Credential Lists" tab of your SIP Domain)

2. Configure Zoiper to Register with Your Twilio SIP Domain #

This is the critical step you're missing. Follow these steps in Zoiper:

• Open Zoiper and tap/click "Add Account"
• Select the SIP account type
• Fill in the account details exactly as follows:
  • Username: +13365518647 (match the number in your TwiML's <Sip> tag—include the + sign!)
  • Password: The password you set when creating your Twilio SIP Credential
  • Domain: branko.sip.us1.twilio.com (your full Twilio SIP Domain address)
• Save the account. Zoiper will attempt to register immediately; if successful, you'll see an "Online" status indicator.

3. Verify Registration Status in Twilio #

Once Zoiper is configured, confirm it's registered with Twilio:

• Go back to your Twilio SIP Domain page
• Navigate to the Registered Users tab—you should see +13365518647 listed here if registration worked.

4. Validate Your TwiML #

Your existing TwiML looks correct, but double-check the <Sip> address matches exactly what you're registering:

<?xml version="1.0" encoding="UTF-8"?>
<Response>
  <Say>Welcome. Your call will be routed to an agent now</Say>
  <Dial>
    <Sip>sip:+13365518647@branko.sip.us1.twilio.com</Sip>
  </Dial>
</Response>

Ensure the username part (+13365518647) is identical to what you used in Zoiper—no typos, missing + signs, or extra characters.

5. Troubleshooting Common Issues #

If registration still fails:

• Check Zoiper's network settings: Make sure your firewall isn't blocking SIP traffic (default port is 5060; Twilio also supports 5061 for TLS)
• Verify your SIP Credential password is correct—sometimes typos happen here!
• Restart Zoiper and your network connection to clear any cached registration issues
• Check Twilio's Debugger for more detailed error logs—this can tell you if the problem is invalid credentials, a missing user, or network-related.

Once your Zoiper is successfully registered with your Twilio SIP Domain, your incoming calls should route correctly after the welcome message.

内容的提问来源于stack exchange，提问作者Gervasius Twinklewinkleson