Hi, only root certificates of certificate authorities will ship in the Firefox trust store by default. Intermediate certs that chain up to a trusted certificate authority are getting cached by Firefox for future use though. If you have a website that isn't trusted by default, it's most likely that the server isn't properly serving the intermediate certificate chained up to the trusted root. Please refer to the support resources of your cert's seller on how to implement that.

You can check the server.

• https://www.ssllabs.com/ssltest/

Hi johnljordan, if you installed the certificate yourself (literally uploaded the file to the server), check your issuer's instructions on whether you need to also upload a bundle file that contains all the necessary intermediate certificates to complete the chain of trust. Usually you do.

If you bought the certificate through CPanel or it was otherwise installed by your web host, point them to your SSLLabs test results and ask them to fix it.