# Device offline

> Get a desk phone or softphone back online when it won't register or keeps disconnecting.

- URL: https://kb.voipcloud.online/au/troubleshooting/device-offline/
- Section: Troubleshooting
- Type: troubleshooting
- Applies to: All countries
- Last reviewed: 2026-11-09

## Symptom

- A desk phone, DECT phone, adapter or softphone shows **Offline** in **PBX** › **Devices**.
- The phone's screen shows "No service", "Registration failed" or similar, or it can't make or receive calls.
- Or the device comes online but drops offline again every so often.

The Webphone mobile app always shows as online, because the PBX can't tell when a smartphone is unreachable. This page is mainly about SIP devices.

## Quick checks

1. **Restart the phone.** Wait until it has fully started, then check its status in **Devices** again.
2. **Did you apply the configuration?** A new device can't register until you click **Apply configuration** on the **PBX** tab.
3. **Is the internet working** at the phone's location? Try a website on a computer connected to the same network.
4. **Is it one phone or all of them?** If every phone at a site is offline, the problem is most likely the internet connection or router.

## Likely causes and fixes

### 1. Wrong SIP details, and the IP address is now blocked

If a device tries to register with the wrong username or password, its public IP address is blocked. The block lifts automatically after 5 minutes. While it's blocked, every phone at that site can be affected.

**Fix:**

1. In **PBX** › **Devices**, open the device and compare its SIP credentials (**Domain**, **Username**, **Password**, **Transport protocol**) with the phone's settings. Copy them with the copy icon rather than retyping.
2. Correct the phone's settings. To stop more failed attempts, you can unplug or switch off the phone while you check.
3. To see whether your IP address is blocked, enter it in **Check IP address for blocking** in the device's details and click **Check**.
4. Wait 5 minutes, then restart the phone.

The IP check is shown in the device's details while the device is offline or blocked.

### 2. The SIP credentials changed

- Turning **TLS encryption** on or off in [General settings](https://kb.voipcloud.online/au/pbx/settings/general-settings/) changes the SIP credentials of every SIP device. Each phone must be set up again with its new details.
- After you generate a new password and apply the configuration, it can take up to 5 minutes before the device can connect with the new credentials.

### 3. The device is locked to an old IP address

If **Allow connection from one IP address only** is on in the device's **Advanced parameters**, the phone can only connect from that public IP address. If your internet provider changed your IP address, or the phone moved, it can't register.

**Fix:** update the IP address, or turn the option off. Save and apply.

### 4. The router or firewall blocks the phone

Routers with SIP ALG turned on, and strict firewalls, often stop phones registering or make them drop offline.

**Fix:** turn off SIP ALG on the router and allow the phone system's traffic through your firewall. See [Network requirements](https://kb.voipcloud.online/au/getting-started/network-requirements/).

### 5. The phone registers, then keeps dropping offline

The router may be closing the phone's connection between registrations. Make the phone check in more often.

On a Yealink phone (web interface):

1. Go to **Account** › **Register**. Under **SIP Server 1**, set **Server Expires** to 120.
2. Go to **Account** › **Advanced**. Set **Keep Alive Type** to **Options** and **Keep Alive Interval (Seconds)** to 30.
3. Click **Confirm**.

For other phones, look for the registration expiry and keep-alive (NAT keep-alive) settings in the manufacturer's guide. See also [Yealink common issues](https://kb.voipcloud.online/au/phones-and-apps/yealink/yealink-common-issues/).

### 6. The internet connection is down or unstable

**Fix:** restart your modem and router, and check your internet provider's outage page. Check **Support** › **Network status** for a known problem on our side.

On the nbn, see [nbn connection issues](https://kb.voipcloud.online/au/troubleshooting/nbn-connection-issues/).

### 7. Softphone error codes

A softphone that shows **401**, **403** or **407** has the wrong username or password. See [Softphone errors](https://kb.voipcloud.online/au/phones-and-apps/softphones/softphone-errors/).

## When to contact support

If the device is still offline, [create a support ticket](https://kb.voipcloud.online/au/support/support-tickets/) with:

- the device name or SIP username shown in **Devices** (never the password);
- the phone's make and model, or the softphone name and version;
- when it went offline, and whether other devices at the same site are online;
- the site's public IP address, and whether anything changed recently (new router, new internet service, moved office);
- what you've already tried.