Start in the app, not the network. Most “no sound” and “they can’t hear me” problems in the 3CX Windows app come from the wrong microphone, speaker, or phone mode. Calls that connect with missing or one-way audio, or calls that never connect, usually point to PBX, firewall, or extension settings that only your administrator can change. This guide separates those cases so you know which fixes are yours and which to hand off.
Pick the right branch first
| Symptom | Most likely area | Who fixes it |
|---|---|---|
| You hear nothing (no ring, no voice) | Speaker or ringer selection, or wrong phone mode | You |
| They can’t hear you | Microphone selection, or headset integration | You |
| Call connects but audio is missing or one-way | Network or PBX audio (RTP) path, if local devices are correct | Administrator |
| Calls won’t connect, especially when remote | Extension remote-access rights, tunnel or firewall configuration | Administrator |
| App starts only in the background or closes immediately | Windows media or runtime components | You or IT, depending on policy |
To narrow it down, note whether the failure affects internal calls, outside calls, or only remote use. This is a diagnostic habit, not a 3CX-published test, but it tells your administrator where to look.
Fix no sound or a silent microphone
1. Select the right audio devices
- In the 3CX Windows app, open the menu and choose Audio Options.
- Under Audio Devices, set Microphone to your headset’s microphone.
- Set Speaker to the headset’s output.
- Set Ringing separately. If you want incoming rings on the PC speakers while calls go to the headset, choose the PC speakers here.
- Place a test call and confirm both directions.
3CX’s end-user troubleshooting guidance (Simple Troubleshooting of the 3CX Apps, published 27 July 2020) gives this as the first remedy for no sound or no voice transmission.
2. Confirm Softphone mode
3CX distinguishes Softphone mode from CTI mode. In CTI mode the app only controls a desk phone, so the audio runs through that phone and not your PC headset. If you expect the PC headset to carry the call, make sure the app is in Softphone mode.
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3. Check Jabra headset integration
3CX’s Jabra setup page (last updated 4 June 2026) covers the Web Client and the Windows softphone. The steps are:
- Install Jabra Direct and connect the headset.
- In the app, go to Settings > Audio/Video > Headset integration and choose Jabra.
- Select the headset as microphone and speaker.
The ringer can use any device you like. Volume and mute control from the headset depend on the model’s capabilities, so a missing button function does not by itself mean a fault.
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Fix calls that connect with missing or one-way audio
If the right devices are selected and the problem remains, treat it as a connection issue. Do not open ports on your own PC for this. The usual causes sit on the PBX and network side, and 3CX says users shouldn’t change advanced settings themselves.
3CX’s firewall guide (last updated 25 September 2026) is written for on-premise systems. It lists these requirements:
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| Purpose | Direction and port |
|---|---|
| SIP signalling | Inbound UDP 5060 and TCP 5060–5061 |
| RTP audio between PBX and provider/trunk | Inbound UDP 9000–10999, with two RTP ports needed per simultaneous call on the described path |
| Remote app tunnel | Inbound UDP and TCP 5090 |
| Remote app presence and provisioning | Inbound TCP 443 or 5001, or the configured HTTPS port |
These apply to the actual release and topology, so your administrator should check them against your deployment and not copy the table blindly.
3CX’s Firewall Checker guide names the common remedies: disable SIP ALG on the router, check port forwarding, and inspect firewall logs. It also checks UDP port forwarding and port preservation, and recommends running the checker after any firewall change. Disabling a firewall wholesale is not a recommended fix; the guide’s Windows firewall note concerns analysis on the 3CX server.
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Fix calls that won’t connect
- Remote users: your extension must be granted remote connection rights. Ask the administrator to verify this.
- Tunnel and provisioning: remote apps depend on the 5090 tunnel and the HTTPS provisioning port listed above, which are administrator-side checks.
- Still failing: 3CX’s guidance is direct: “If you still face issues and are unable to make or receive calls after trying these troubleshooting tips, consult your administrator.”
Fix an app that starts in the background or closes immediately
Use this section only if your symptom matches. These are privileged, version-dependent system changes, so follow your IT policy and 3CX’s Windows Softphone issue page (last updated 28 July 2026) for the exact steps.
App runs only in the background
Open the app log and look for a FileNotFoundException referencing Windows.Media.Playback.MediaPlayer. If it is present, 3CX’s documented fix is to enable Windows Media Features and Windows Media Player Legacy, reboot, and, if needed, run the PowerShell capability command given on that page.
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App closes immediately
Check the AppxDeploymentServer event log in Event Viewer for the Windows App Runtime Singleton failure pattern the article describes. The remedy is to match the installed app package version with the corresponding Windows App SDK runtime. These repairs do not address call audio, so don’t run them for a sound problem.
What to send your administrator
- Whether you were on Softphone or CTI mode, and the headset model.
- Whether the failure hits internal calls, outside calls, or only remote use.
- Whether audio is absent in both directions or just one.
- Whether you are in the office or remote, and on which network.
- Any app log or Event Viewer error text, for startup problems.
Labels and remedies can vary with your 3CX version, Windows edition, headset, and network layout. The vendor documentation above does not diagnose individual PCs or PBX systems.
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