Error code

Firefox SSL_ERROR_NO_CYPHER_OVERLAP

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

What it means

Firefox and the server could not agree on any shared encryption algorithms.

How to fix it

  1. Update the server to support TLS 1.2 or 1.3 with modern cipher suites.
  2. If you manage the server enable at least one cipher from Firefox's supported list.
  3. This error usually indicates the server is outdated and needs an SSL/TLS upgrade.

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