Error code

Firefox SEC_ERROR_OCSP_INVALID_SIGNING_CERT

FIREFOXSEC_ERROR_OCSP_INVALID_SIGNING_CERT
Browser Error Code· An error code shown in a web browser when a page fails to load.

What it means

The certificate that signed the OCSP response is not trusted.

How to fix it

  1. Retry the connection as this is sometimes a transient OCSP lookup failure.
  2. Contact the site owner if the problem is persistent as their OCSP responder may be misconfigured.

Not affiliated with Firefox. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.