SIP 401 Unauthorized Error
The SIP client 401 Unauthorized error means that the telephony server has rejected the authentication request. In most cases, this happens due to incorrect SIP account credentials, such as a wrong server address, username, password, or other connection settings.
Main Causes of the 401 Unauthorized SIP Error
- Incorrect SIP account credentials (username, password, domain/server)
- Typos when entering configuration settings
- Use of outdated or changed login details
- Simultaneous registration of the same SIP account on multiple devices
- Restrictions from the SIP provider or PBX system
How to Fix the 401 Unauthorized Error
Check SIP Settings
Make sure the following details are entered correctly:
- SIP server address
- Username (login)
- Password
- Port and protocol (if required)
Verify with Your Provider
Use only the current configuration details provided by your VoIP service provider.
Check the Number of Connections
Some SIP servers do not allow the same account to be registered on multiple devices at the same time.
Restart the SIP Client or Device
This can help reset an incorrect authentication session.
Contact PBX
If the issue persists, contact your PBX administrator or your provider’s technical support team—they can identify the exact cause of the authentication failure.
The 401 Unauthorized error in a softphone is almost always related to authentication issues. In most cases, it can be resolved by verifying the account credentials. If the problem continues, the cause may be on the server side, and assistance from your telephony provider will be required.