All cause codes appear due to zero-second calls: calls that are never fully established. Some of these codes are more serious than others. If it seems like you're having issues on calls that don't have a cause code associated with them, that's possible, specially if you're having trouble with calls after they're answered. Below is a chart of cause codes and their severity. Generally you don't have to take action on INFO/WARN severity levels, but ERRORs and above warrant further investigation.

Cause Code 1

On outbound calls, you will most likely see this error due to a misdial. Check that you're dialing a valid number, maybe by calling it from a landline or cell phone.

On inbound calls, this means your device doesn't have inbound call routing set up for the number dialed. We use the format 1NXXNXXXXXX - see the our guide for your device for more info.

Cause Code 16

The sender hung up the call before the receiver answered. Normally this is not serious, but calls to fax machines should pick up within about 5 seconds.

Cause Code 17

Receiver sent a busy signal - all its channels are in use. Fax machines reattempt the call later, usually in about 5 minutes. Most fax machines only have a single analog line connected to them: if they're called while already sending or receiving a fax, they will issue a busy signal. This error is very common and usually benign.

Cause Code 18

This error is only seen on outbound or forwarded inbound calls, and indicates that we didn't receive ringback from the receiver. For outbound calls, try calling from a landline or cell phone. Otherwise, report this one to us.

Cause Code 19

From the end user perspective, the same as a cause code 41.

Cause Code 21

A generic error from the telephone network - contact us.

Cause Code 27

This is a service-affecting error affecting only inbound calls. It can happen for two reasons:

• Your device wasn't registered to your trunk when this call occurred. In some cases your device will reconnect to the trunk later on, so when you log onto the portal you will see that trunk has a device connected even though it received a 27 error in the past. If you see this happening, try decreasing the registration interval to 5-10 minutes. Most of our device guides recommend this already.
• Someone called a number on your account that isn't assigned to a trunk. You can assign the number to one of your trunks through the portal to clear this error.

Cause Code 28

Indicates that the dialed number isn't offered under our dial plan. This cause code can occur if the number is misdialed, if the dialed area code isn't allocated on the telephone network, or if you're dialing an international number.

Cause Code 38

A generic error from the telephone network - contact us.

Cause Code 41

Our switch hit the call setup timeout and disconnected the call. This is a service-affecting error mostly affecting inbound calls.

On inbound calls, there are three reasons for this:

• We didn't receive a response to our call setup message from your device after 6 seconds. This usually occurs for customers using IP authentication and indicates either a firewall blockage or that your IP has changed.
• We did receive a response from your device, but the call wasn't answered after 30 seconds. Commonly seen with analog gateways, this usually means the fax machine is set to manual answer mode or is plugged into the wrong ATA port.
• Rarely, this cause code indicates that we received a response to our call setup message from your device, but your device didn't start ringing for 7 seconds.

If you get this error message on an outbound call, verify that the number dialed is a fax number, perhaps by calling from a landline or cell phone. Most fax machines pick up within 5 seconds.

Cause Code 42

This is a general code indicating that we couldn't find a route for the call, but a route may become available later. Calling from a landline or cell phone is a good test if you're sure the number should be reachable.