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In the failing code, the certificate is stored as a PROGMEM string with inconsistent indentation. Ensure that lines between -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- are on separate lines, without leading spaces.
Refer to this working example for guidance: ESP32 does connect to the server.
Hope this helps! Let me know if you have any questions.
Best,
Dasha from the HiveMQ Team