Hello @Veilleux, Wayne,
welcome to this moderated Azure community forum.
Azure IoT Edge makes use of several (sometimes optional) certificates.
For example, a certificate could be used as the identity for the IoT Hub registration (opposite to eg. a symmetric key).
Then there is the TLS certificate for securing the transport of the messages between Egde and IoT Hub. This is managed by the operating system.
Last but not least, the communication between Azure IoT Edge modules (and potentially child devices) is also secured using a TLS certificate.
When you create an Azure IoT Edge runtime for the first time, you get a temporary 90 days TLS certificate.
When it expired, you need to restart the edge again for a new 90 days certificate.
For production, it's better to replace this or fix the config.yaml for this (see also the side note in this blog post).
Please perform a 'check' or look at the first log lines of the edgeAgent module te see if that certificate has expired.
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