Session Expired / "Cookie check failed" message showing for non-logged-in users (with FlyingPress cache)

Hello Fluent Community team / members,

I’m running FluentCommunity in a subdirectory at https://example.com/community. I’m seeing a persistent problem where non-logged-in visitors get a modal saying “Session Expired — Cookie check failed” when they visit the community. (I’ve attached a screenshot showing the modal.)

Environment & what I use

• WordPress + FluentCommunity installed at /community (subdirectory).
• Cache plugin: FlyingPress.
• CDN: FlyingCDN.
• DNS: Cloudflare used only as DNS (grey cloud) — Cloudflare is not proxying/caching the site.

Symptoms & behaviour

• When I visit /community as a non-logged-in user, the modal appears immediately: Session Expired / Cookie check failed.
• If I clear FlyingPress cache (and browser), the community works correctly for a while (minutes–hours). After some time the error returns.
• The problem seems linked to when FlyingPress caches many pages (I noticed it after ~600+ pages cached). It looks like some cached response is preventing the cookie/session check from working reliably.

What I have already tried (FlyingPress settings)

• Added these URL / route exclusions:

  • /wp-admin/admin-ajax.php
  • /wp-json/fluent-community/*

• Added these cookie bypass / cookie names in FlyingPress:

  • wordpress_logged_in
  • wordpress_logged_in_

Anything you can tell me about exact cookie names or the minimal set of endpoints to exempt from full-page caching would be extremely helpful. I’m happy to try any recommended headers, exclusions, or short code snippets (functions.php) you provide. Thank you in advance.