The "Missing or Invalid Token" message is the result of the web browser's cookie permissions. Please be advised that if you are having this trouble with the shopping cart to do the following:
1. Open the Settings app and go to Safari > Privacy & Security.
2. Toggle the following options to the Off position. (i.e not green) - Prevent Cross-Site Tracking - Block All Cookies
3. Open the Safari app and try placing an order.
It may be necessary to force quit Safari first, then re-open it to activate the modified options.