If you are using the "Simple Cache" plugin, you may encounter some issues with upsell page when running the funnel pages. This is due to aggressive page caching (which is a good thing!), but it can be easily resolved by excluding the offer page URI from the cache plugin.
You need to exclude offer pages by following these instructions:
Step 1: Note down the slug of your offer page from the general settings
Step 2: Open the settings of "Simple Cache" under the settings tab.
Step 3: See the dropdown right side of this simple cache option page "Enable Advanced Mode"
Step 4: Change the option to "Yes" to have advance mode settings.
Step 5: Locate the option "Exception URL(s)" on the left side.
Step 6: To exclude “offer” pages enter your noted offer page slug (from step 1) as shown in screenshot: /offer/*
Step 7: Scroll down the page and click on the "Save Changes" button to update the settings.
By default, the upsell pages slug is "offer". If you had changed the offer pages slug for any reason get the slug from WooFunnels > Settings > General > Permalinks.