Fix 419 Login Error

My self-hosted CRM is built in plain PHP—no Laravel, no CodeIgniter. The login page has suddenly started throwing a 419 error and I’m convinced the culprit is a broken CSRF token check. I haven’t touched the code or server config recently, so whatever has gone wrong is buried in the existing session or token logic.

I need someone who can jump in right away, trace the issue, and patch it without disabling the CSRF protection. When you’re done I want to log in normally, see no 419, and still have the same level of security. A short note or inline comments explaining what you changed is all the documentation I need.

If you know your way around PHP sessions, tokens, and headers, this should be a quick win.