Telemetry data not being sent to cloud AIOPS, reason: CDL Receiver Key Empty

• Failed to send telemetry data with error: CDL Receiver Key Empty.

> show device-telemetry stats all

Device Telemetry Statistics:
    device-health-performance: 
        last-attempt: Mon Sep  4 10:21:03 CEST 2023
        last-success: N/A
        num-of-failed-attempts: 568
        reason: CDL Receiver Key Empty
        status: failed
    product-usage: 
        last-attempt: Mon Sep  4 10:21:03 CEST 2023
        last-success: N/A
        num-of-failed-attempts: 568
        reason: CDL Receiver Key Empty
        status: failed
    threat-prevention: 
        last-attempt: Mon Sep  4 10:21:03 CEST 2023
        last-success: N/A
        num-of-failed-attempts: 568
        reason: CDL Receiver Key Empty
        status: failed

• Connection against the AIOPS server is getting closed in the SSL handshake, right after the Client Hello.

var/log/pan/device_telemetry_curl.log:

2023-09-04 03:21:03,114 dt INFO S1: CDL: RSP KEY ERR CODE: ['Note: Unnecessary use of -X or --request, POST is already inferred.
....
'* Establish HTTP proxy tunnel to br-prd1.de1.ew3.cdl.paloaltonetworks.com:443',
....
'* OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to br-prd1.de1.ew3.cdl.paloaltonetworks.com:443
'  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0',
'* Closing connection 0',
'curl: (35) OpenSSL SSL_connect: SSL_ERROR_SYSCALL in connection to br-prd1.de1.ew3.cdl.paloaltonetworks.com:443']  

• Any Palo Alto Networks Firewall or Panorama
• Any PAN-OS version

• Domains Required for AIOps for NGFW: https://docs.paloaltonetworks.com/aiops/aiops-for-ngfw/get-started-with-aiops/fqdns
• TCP Ports and FQDNs Required for Cortex Data Lake: https://docs.paloaltonetworks.com/cortex/cortex-data-lake/cortex-data-lake-getting-started/get-started-with-cortex-data-lake/ports-and-fqdns