Home app no longer recognizing any devices

After updating to iOS 18, my iPhone 14 Pro no longer recognizes devices in the Home app. I have HomePods, Meross switches, iDevice switches and Apple TVs. Except for the Homepods, all the others are showing as "No Response." I deleted one of them (a Meross switch) and tried to add it again, but it says "Accessory Already in Another Home" but there is no other home. I don't get it. What would cause this? How can I get these devices to work again?