"Secure Connection Failed . . . Certificate . . . is invalid."

Firefox claims certificate is invalid.

Try IBM's simple fix:

1. Type about:config in the Firefox address bar to access Advance settings. Read the warning presented, and then click the "I'll be careful, I promise" prompt to accept and proceed.
2. Scroll down to security.use_mozillapkix_verification and set it to false. Double-click to toggle its value (or, right-click on it and select Toggle)

Firefox has had this intermittent error since version 31.0. The simplest solution is to use an earlier version of Firefox.

IBM has more suggestions.

Firefox Error codes:

• sec_error_extension_value_invalid
• sec_error_ca_cert_invalid
• sec_error_unknown_issuer