The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.

I am trying to browse websites through a proxy that intercepts the TLS connections and signs the certificates using a private CA certificate. If I'm using only a root CA certificate, setting it on my proxy as well as in the OS's certificates store, I can browse the internet without any issues. The chains in this case would be: Root CA -> Server Certificates However, my setup mandates that I use an intermediate CA on the proxy. The chains in this case would be: Root CA -> Intermediate CA -> Server Certificates If I add an intermediate CA to the proxy and the root CA to my OS's certificates store, I get the following error: " Secure Connection Failed An error occurred during a connection to www.youtube.com. Peer’s certificate has an invalid signature. Error code: SEC_ERROR_BAD_SIGNATURE The page you are trying to view cannot be shown because the authenticity of the received data could not be verified. Please contact the website owners to inform them of this problem. " I'm using Firefox 82.0.2 on Windows 10. How can I get more details on why it's failing? I've tried looking in the "Security" tools tab, but I see only this error ID. Thank you, Cosmin