If the green "+" to add a plan is missing, log out by clicking your username, then return to the plans page to see the "+" and add the plan to your cart.
If you do not see the green “ + “ symbol to add the plan to your shopping cart, please log out of your account by clicking on your username, then “log out”. You can then go back to the plans page and click on the plan you want to purchase. You should now see the green “ + “ to add the plan to your shopping cart.