Notify doesn't work anymore when passed a list of people

When running formula Notify(Todos.Filter(Done = false).Who.Unique(), "One hour until meeting. Review Todos and add issues ❤️")

I get the error message:

Notify expects parameter people to be a row, a list of rows, or a column, but found value ('Preston, Hunter, Connor, Maureen '), which is a list of people

Why wouldn’t notify work on a list of people? This used to work.