what I learned from this thread is that you should keep refreshing about 10 minutes prior to 10pm and 10 minutes after.
at first I was unsure what everyone meant by refreshing, but I found that on the website version, once you have that pop up that asks you to enter your zip code to show the nearby stores, keep hitting "LOCATE". you may notice every time you hit this button, the green "check out" button in the background flashes.
I kept doing this and started losing confidence when "unavailable for pick up" was all I saw. but around 10:05, it finally turned green and said "in stock".
Once you see this, do not hesitate to pick the store and update your cart.
as people said, its highly recommended you have "Express Checkout" turned on. you should ensure this is on before you even get to the screen that allows you to enter your zip.
I sped through as fast as I could and cannot remember exactly the screens that followed, but I do remember it asks for your phone number (optional as to call you when ready, but they will email you anyway), and to enter the security code on the back of your CC. so either you have the CC next to you or remember that 3 digit code. then just keep proceeding and if you get to the last screen telling you they're processing your order, you are golden.
I hope this helps anyone who is sort of new to trying the reservation system as I was. good luck