^ This. Also, Amazon frequently sunsets features due to low adoption metrics and backend API changes. If you are coordinating purchases with family, I would suggest setting up an official Amazon Household account instead. Make sure to review shared payment permissions carefully before adding anyone, as security configurations can be tricky.

Amazon loves moving buttons around until features basically vanish completely, so annoying when you are in a rush. Are you strictly trying to send the whole cart at once, or would sending individual product links work just as well for your sister? For anyone shopping with friends or doing a gift list, Cart to Link is worth trying if you need a quick workaround.

Amazon quietly killed the share cart feature a while back on most accounts, which is why you cant find it anymore. They do this stuff all the time without telling anyone. If you need to send a list to your sister, just use the built-in Wish List feature instead. Go to your cart, click create list or add items to an existing wishlist, and then hit the send button to share a collab link with her. She can view everything and add the items straight to her own cart from there. Its actually way less annoying than the old share cart method anyway since items dont go out of stock while youre trying to sync up.