Devices showing up as "This device is unavailable at the moment"

I have five smart bulbs, two Samsung Multipurpose sensors, and a Samsung Motion sensor that have all went offline with a message in the Smart Things app that says “This device is unavailable at the moment.” I have replaced batteries, removed the devices from the hub, reconnected them to the hub. After a day or so, they disconnect again. What should I do to rectify this situation.

Did your hub receive an update recently? Are you on 18.18 or 18.20 or 18.21?

Since you are using mostly Samsung devices this is probably not your issue but worth checking.