# Softphone errors

> What SIP error codes 401, 403, 404, 407 and 488 mean on a softphone or desk phone, and how to fix them.

- URL: https://kb.voipcloud.online/phones-and-apps/softphones/softphone-errors/
- Section: Phones and apps › Softphones
- Type: troubleshooting
- Applies to: All countries
- Last reviewed: 2026-11-09

Softphones and SIP phones show a number when something goes wrong. Find the code below. Most problems come from a SIP detail typed wrongly.

To check the details, open **Devices** at the top of the **PBX** tab, select the device and compare its **SIP credentials** (**Domain**, **Username** and **Password**) with your app.

## 401 Unauthorized

**Cause:** the username or password is wrong.

**Fix:** copy the **Username** and **Password** again from the device's SIP credentials. If you changed the password with **Generate a new password**, apply the configuration and update the app. It can take up to 5 minutes to connect with new credentials.

## 403 Forbidden

**Likely causes:**

- The username or password is wrong.
- The device may be temporarily blocked after registering with a wrong password. The block lifts after 5 minutes.
- In Bria on a phone, **Registration Mode** is set to **Single Device Takeover**.

**Fix:** correct the details and wait 5 minutes before trying again. While the device is offline or blocked, its settings in **Devices** show **Check IP address for blocking**: enter your public IP address and click **Check** to see whether it's blocked. For Bria, see [Bria Solo](https://kb.voipcloud.online/phones-and-apps/softphones/bria-solo/).


## 404 Not Found

**Cause:** the number you dialled doesn't exist or was dialled in the wrong format.

**Fix:** check the number, and try calling it from another phone. See [Cannot make outbound calls](https://kb.voipcloud.online/troubleshooting/cannot-make-outbound-calls/).

## 407 Proxy Authentication Required

**Cause:** the username or password is wrong.

**Fix:** same as 401: copy the SIP credentials again.

## 488 Not Acceptable Here

**Cause:** the phone is connected, but its audio codecs don't match the PBX.

**Fix:** in your app's codec settings, enable only codecs the PBX supports: Opus, G.722, G.711 a-law and G.711 u-law. Remove G.729. The device's settings in **Devices** list its codecs under **Supported audio codecs**.

## The device stays offline with no error

- Check the **Domain** includes the colon and port.
- Set the transport to the **Transport protocol** shown in the device's SIP details (TCP, or TLS if TLS encryption is on).
- Make sure the SIP device isn't also signed in on another app or phone.
- Check that your network allows SIP traffic and that SIP ALG is off on your router. See [Network requirements](https://kb.voipcloud.online/getting-started/network-requirements/).

## When to contact support

If the error continues after these checks, [raise a support ticket](https://kb.voipcloud.online/support/support-tickets/). Include the error code, the app and version, the SIP device's name, and the time you last tried. Never send your SIP password.

## Related

- [Device offline](https://kb.voipcloud.online/troubleshooting/device-offline/)
- [Devices](https://kb.voipcloud.online/pbx/settings/devices/)