If a Microsoft Teams Phone user is unable to call out, there are several possible causes. Below is a detailed guide to troubleshoot and resolve the issue.
🔍 1. Check the Basics
1.1 Verify Internet and Teams Connectivity
- Confirm the device has a stable internet connection.
- Ensure Teams can connect to Microsoft 365 services — no errors or “offline” messages.
- Test with another user or device to rule out general network issues.
1.2 Verify User License and Assignment
Teams calling features depend on the right licensing:
- The user must have one of the following:
- Microsoft 365 E5, or
- Microsoft 365 E3 + Teams Phone Standard add-on, or
- Business Voice license (for SMB environments)
- If using Calling Plans, ensure:
- A Phone System license and Calling Plan license are both assigned.
- The license changes are synced (can take 15–60 minutes).
To verify:
- Go to Microsoft 365 Admin Center → Users → Active users.
- Select the affected user.
- Under Licenses and Apps, confirm the phone-related licenses are active.
⚙️ 2. Check Teams Admin Center Settings
2.1 Voice Routing Policies
- Go to Teams Admin Center → Voice → Voice routing policies.
- Ensure the user has a valid voice routing policy assigned.
- If Direct Routing is used, check the assigned route includes valid SBC (Session Border Controller).
2.2 Dial Plan
- Verify the user’s dial plan matches their location or region.
- Ensure normalization rules are correct (e.g.,
+1for US calls).
2.3 Emergency Location
- For compliance, an emergency location must be configured.
- Go to Voice → Emergency policies and confirm the user’s policy and location.
🧩 3. Direct Routing / SBC Checks (if applicable)
If you’re using Direct Routing:
- Verify SBC connectivity in the Teams Admin Center → Voice → Direct Routing.
- Ensure the SBC certificate is valid and not expired.
- Confirm SIP signaling is allowed through your firewall and ports (typically 5061 TCP).
- Review the SBC logs for call setup or TLS negotiation failures.
☎️ 4. Call Analytics and Logs
4.1 Review Call History
- Open Teams Admin Center → Users → [User] → Call history.
- Look for failed call attempts and error codes.
Common examples:
| Error Code | Description | Possible Cause |
|---|---|---|
403 Forbidden | Call not allowed | No voice policy or routing issue |
404 Not Found | Invalid number | Dial plan issue |
486 Busy Here | Destination busy | Recipient line busy or routing issue |
503 Service Unavailable | SBC or PSTN carrier issue | Connectivity or configuration problem |
🔐 5. Network and Firewall Requirements
Ensure all required ports are open:
- UDP 3478–3481 for media (STUN, TURN, SRTP)
- TCP 80, 443 for signaling and APIs
- TCP 5061 for Direct Routing (SIP TLS)
- Verify QoS settings are applied for audio traffic to reduce call drops or failures.
🧭 6. Test with Teams Web and Desktop App
- Try calling from the Teams web app (
https://teams.microsoft.com) to isolate client issues. - If calls work in the browser but not the desktop app:
- Clear Teams cache:
%appdata%\Microsoft\Teams - Restart Teams and re-test.
- Clear Teams cache:
🧰 7. PowerShell Verification
You can confirm configuration using Teams PowerShell:
# Connect to Teams PowerShell
Connect-MicrosoftTeams
# Check user’s voice routing policy
Get-CsOnlineUser -Identity user@domain.com | Select-Object DisplayName, LineURI, EnterpriseVoiceEnabled, VoiceRoutingPolicy
Ensure:
EnterpriseVoiceEnabled=TrueLineURIis properly formatted (tel:+1234567890)
🚨 8. External Factors
If the environment uses:
- Operator Connect: Contact your provider to verify provisioning and number activation.
- Calling Plan (Microsoft): Check for service outages at Microsoft 365 Service Health.
✅ 9. Quick Fix Summary
| Issue | Fix |
|---|---|
| Missing license | Assign Teams Phone license |
| No dial plan | Assign correct dial plan |
| SBC issue | Verify TLS certificate and SIP routing |
| User can receive but not make calls | Check outbound voice routing policy |
| Web app works, desktop fails | Clear Teams cache and restart |
