The ThingSpeak certificate was updated recently. If you are using secure communication for your devices, you may need to update the certificate or certificate fingerprint on your devices. Secure ThingSpeak communications and security certificate If anyone find a working with ThingSpeak root certificat for Arduino ESP32 programmation, I'd be interrested, something like : const char* rootCACertificate = "-----BEGIN CERTIFICATE-----\n" ... here should be what I need ... "-----END CERTIFICATE-----"; for Arduino code: WiFiClientSecure client; client.setCACert(rootCACertificate); Thanks, TC This post might help. Hi, Thanks, but I already tried the one exported and download from ThingSpeak.com, still not working. I try also the one from Digicert and two others, none are working. I am hoping somehting from the other post... TT Use firefox Got to thingspeak.com. Click on the lock icon Click on Connection secure -> More information Click on view certificate Click on "DigiCert Global Root CA" in the tab Click on PEM(cert) under Miscellaneous Right click on the downloaded file. Open with any editor. In Chrome, I think its similar, but you want to save it with base64 encoding. I was able to use the thingspeak library secure connection with esp32 with this cert, but you need to add the line you mentioned. in secrets.h: client.setCACert(SECRET_TS_ROOT_CA); #define SECRET_TS_ROOT_CA "-----BEGIN CERTIFICATE-----\n" \ ... "-----END CERTIFICATE-----\n" in main file: const char* certificate = SECRET_TS_ROOT_CA; % in setup fucntion client.setCACert(certificate); // Set Root Certificate for authenticity check http mqtt secure certificat