The hostname sent by the client or browser via Server Name Indication (SNI) does not match the request host header. It is commonly caused by the following:
- your local browser setting the incorrect SNI host header
- a network proxying SSL traffic caused a mismatch between SNI and the Host header of the request.
Test for an SNI mismatch via an online tool such as: SSL Shopper.
Provide Cloudflare Support the following information:
- A HAR file captured while duplicating the error