# 32022: ACK not received from your SIP endpoint

Log Type: APPLICATION

Log Level: ERROR

## Description

Twilio sent a `200 OK` response for an inbound SIP call and did not receive an `ACK` from your SIP endpoint within 32 seconds. Twilio then terminated the call. SIP requires the calling endpoint to acknowledge a `200 OK` to complete call setup.

### Possible causes

* Your NAT configuration is preventing the `ACK` from reaching Twilio.
* Your firewall is blocking SIP signaling traffic.
* Your SIP endpoint is sending the `ACK` to the wrong IP address, or building the `ACK` with an incorrect `Request-URI` or `Route` headers.
* Your SIP infrastructure is rewriting Twilio IP addresses in the `ACK` or related SIP headers, which prevents Twilio from processing the request.
* Packet loss or another network disruption between your network and Twilio caused the `ACK` to be lost.

### Possible solutions

* Review your SIP endpoint configuration and confirm that it sends an `ACK` after Twilio returns `200 OK`.
* Review your SIP endpoint logs to verify whether the `ACK` was generated, where it was sent, and whether any NAT or firewall handling changed the request.
* Build the `ACK` using the IP address in the `Contact` header of Twilio's `200 OK` as the `Request-URI`. Send the request to the IP address in the `Record-Route` header from the same `200 OK`.
* Do not replace Twilio IP addresses in the `ACK` URI or headers. Rewrite only your own addresses when your network requires NAT handling.
* Make sure your SIP device is configured to use the maximum supported retransmissions for SIP signaling.
* Review the call record in Console and download the SIP PCAP. If possible, capture a PCAP on your SIP endpoint and compare both traces to find where signaling diverges.

#### Additional resources

* [Use SIP with Twilio Voice](/docs/voice/api/sip-interface)
* [Inbound - Sending SIP to Twilio](/docs/voice/api/sending-sip)
* [Troubleshooting your Trunk](/docs/sip-trunking/troubleshooting)