The simple shopping cart plugin was designed to work with the W3 Total Cache plugin.
Integration Steps for W3 Total Cache Plugin
Step 1) Go to the “Page Cache” menu in your W3 Total Cache plugin.
Step 2) Add the following line in the “Rejected Cookies” field under the “Page Cache” settings menu of the W3 Total Cache plugin and all done:
Where is the “Page Cache” menu in W3 Total Cache Plugin?
The folloiwng screenshot will tell you where to find the page cache menu:
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