Hi, good day!, I am haviong exactly the same issue. I am trying to skip cert verification because I got thus exact error, and when I disable the cert verification...I receive the same answer.
I am not sure if I missed something but I post it here because I am seeing that this had never an answer ...

Hi, good day for all!
I am trying to make work the Advanced OTA example, with a .bin obtained from building the hello_world example, exactly as it appears in the documentation. I could make the OTA server, the certs, I do keep control of the version of the firmware, I am flashing, and my device is a ...