Cause: Your WordPress permalink structure is not set to "Post Name," or rewrite rules are stale.
Fix:
Go to Settings → Permalinks in your WordPress admin.
Select Post Name (the option that shows /%postname%/).
Click Save Changes.
Try visiting a funnel URL again. It should now load correctly.
Tip: Even if permalinks were already set to Post Name, try clicking Save Changes anyway. This flushes the rewrite rules and can fix 404 errors caused by caching or plugin conflicts. The plugin also auto-flushes rewrite rules on activation.