| Denied by callback | Callback response denied the verification. |
| Invalid callback | Callback was invalid. |
| Internal error | Internal server error. |
| Destination denied | Verification destination denied. |
| Fraud | Fraudulent activity. |
| Not enough credit | Not enough credit in dashboard account. |
| Blocked | Blocked number. |
| Network error or number unreachable | Network error or destination number is otherwise unreachable. |
| Failed pending | Pending failure. |
| SMS delivery failure | Could not deliver SMS. |
| Invalid CLI | CLI is invalid. |
| Invalid code | Input code is invalid. |
| Expired | Verification request has expired. |
| Hung up without entering valid code | Phone call ended without entering code. |