A lot of our customers are complaining that they add stuff to the cart & then when they proceed to checkout they are redirected to an empty cart.
We thought that it might be a result of too short session time, so we tried increasing the cookie/session lifetime to 86400 (on both admin & server).
After that, I tried to reproduce the problem & managed to achieve the weird behavior as you can see on the attached screenshot.
I added products to cart, came back after about 20-30 minutes & saw my items in the minicart. then I proceeded to checkout & it redirected me to this empty cart while the minicart is still showing my items (refreshing the page also didn't work):
-- Any Idea?
UPDATE: So far we managed to solve this issue by changing back the session configuration to use files (disabled Memcached). I know that Magento recommends using Memcached & have no idea what caused this issue...