Hi @wfpeter,
I have the exact same issue and it’s clearly a conflict between Yoast and Wordfence, I contacted Yoast support and here’s what they said:
“We’d still expect Yoast to work with WordFence. However, as WordFence sometimes modifies parts of the server for security purposes, it takes some additional steps and configuration to make it work with Yoast…we’d recommend you work directly with WordFence to resolve the issue, as there is the expectation that the WordFence plugin needs to be configured first to be able to work with Yoast.”
Yoast works fine on staging (where Wordfence is not installed) but on production where we have Worfence, it just returns this error and redirections returns 500:
PHP Fatal error: Uncaught Error: Undefined constant "SECURE_AUTH_COOKIE"
Please look into and let me know if there is an extra configuration to do.
