---
title: "Troubleshoot"
source_url: https://dev.digicert.com/trustcore-sdk/nanomqtt/troubleshoot.html
---

| Symptom | Likely cause | Resolution |
| --- | --- | --- |
| **CONNACK 0x95 “Packet too large”** | Broker rejects the packet size. | Reduce payload size or set `max_packet_size` in the MQTT 5 *CONNECT* properties. |
| **No incoming PINGRESP** | Application traffic is more frequent than the keep-alive interval. | This is expected — the broker resets the timer whenever data flows. |
| **Retained message not cleared** | Message published without clearing retain flag. | Republish the same topic with an empty payload and `--mqtt_pub_retain`. |
| **TLS handshake fails** | CA bundle missing or host-name mismatch. | Verify `--ssl_ca_file` or (for tests) add `--ssl_allow_untrusted`. |
| **Session resume not working** | `--mqtt_clean_start` flag still set. | Omit `--mqtt_clean_start` and set a non-zero `--mqtt_session_expiry_interval`. |


> **Tip**
>
> Use `--print_hex_bytes` to view raw payload bytes when debugging encoding issues.