If you are using the "Simple Cache" plugin, you may encounter some issues 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 URI 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 general settings
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Step 2: Open the settings of "Simple Cache" under the settings tab.
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Step 3: See the dropdown right side of this simple cache option page "Enable Advanced Mode"
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Step 4: Change the option to "Yes" to have advance mode settings.
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Step 5: Locate the option "Exception URL(s)" on the left side.
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Step 6: To exclude “checkouts” pages enter your noted checkout page slug (from step 1) as shown in the screenshot: /checkouts/*
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Step 7: Scroll down the page and click on the "Save Changes" button to update the settings.
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By default, the Checkout page's slug is "checkouts". If you had changed the checkout pages slug for any reason get the slug from FunnelKit (formerly WooFunnels) > Settings > General > Permalinks