Google Assistant can't add items to shopping lists

This issue started at least a few weeks ago.

I have multiple lists on https://shoppinglist.google.com/. Usually, I can ask the Google Assistant to add an item to a specific list and it will Just Do It™. At some point, however, it stopped working. Now, when I ask Google Assistant to add an item to a list, it'll say "Item added to list SHOPPING". I do have a list called "Shopping", but it responds this way no matter which list I asked it to add the item to. Not only that, but it doesn't add the item to any of my lists.

If I am using Google Assistant's text input to ask it to add an item to a shopping list, the "View List" link it provides either takes me to an error page ("Can't load page."; this happens on my phone) or takes me to https://www.google.com/ (this happens on my Chromebook).

This issue is occurring on my Chromebook, my Android phone, and all of my Home/Mini/Nest speakers.

Things I've tried:

Per https://support.google.com/googlenest/answer/7211942?hl=en. No dice. I am out of ideas.

Screenshot of the error occurring on my phone:

Screenshot of the page "View List" takes me to on my phone:

Screenshot of the error occurring on my Chromebook: