The device suddenly lost access to MQTT

[AntonKozlenko]

Thank you for the complete answer.

I also wanted to note one observation in the OTA process.

The dashboard shows that OTA is rejected, but the behavior of the device shows that the new firmware has been successfully downloaded and updated. The device is running on the new firmware.

The port monitor shows only such messages:
E (530128) TRANSPORT_BASE: poll_read select error 113, errno = Software caused connection abort, fd = 48
E (530128) MQTT_CLIENT: Poll read error: 119, aborting connection

I use Arduino IDE

Below is a screenshot from the dashboard.

[AntonKozlenko]

Screenshot from dashboard

[ESP_Piyush]

The log message seems to be incomplete. Since app rollback is enabled by default, when the node reboots into new firmware, it waits for an MQTT connection before it can report OTA success. If it cannot connect or there is some crash, it boots back into older firmware and reports rejected saying that the firmware rolled back. Can you check the subsequent logs to see if this is what has happened?

[AntonKozlenko]

There are no error messages in Arduino during subsequent reboots.
The device is loaded on an already NEW firmware (which was allegedly rejected).

I have tested this on two devices: ESP32 (16Mb) and ESP32 S3 (8Mb) .