Flagged folder in Mac Mail not working
I have Mac mail set up with just my iCloud mail account.
There's a "Flagged" folder that has been there for years, with subfolders for each flag colour.
However, if I unflag emails, they don't disappear from that folder (despite restarting Mail or MacOS).
When I log in at iCloud.com, I noticed this folder doesn't exist at all, and you can only add flags of one colour to emails. There's also no equivalent folder that shows flagged emails.
Has this feature been deprecated, or is there a way to restore it to working order?
Mac mini (M2, 2023)