Information about website upgrade

My trolley was full the last time I was shopping but now my trolley is empty. Why did this happen? As we are upgrading the site, any items saved in your trolley will no longer be there if your store has recently upgraded.
Do I need to download the new SuperValu online shopping app or will it update itself? Your SuperValu App will automatically update once the new app becomes available. If your phone settings are adjusted to manually update please insure you have updated the latest version of the app.