If you are using the "WP Rocket" plugin, you may encounter some issues with Aero/the Funnel Builder Checkout page when visiting the checkout. This is due to aggressive page caching (which is a good thing!), but it can be easily resolved by excluding the checkout page URL from the cache plugin.
You need to exclude checkout pages by following these instructions-
Step 1: Note down the slug of your checkout page from the WooFunnels general settings tab
Step 2: Open the settings of “WP Rocket” and click on "Advanced" tab.
Step 3: To exclude "checkouts" pages enter your noted checkout page slug (from step 1) with special characters as shown in screenshot: "/checkouts/(.*)
Once done, click on "Save Changes".
Note: By default, Checkout page's slug is "checkouts". If you had changed the checkout pages slug for any reason get the slug from WooFunnels > Settings > General > Permalinks