already tried everything ,,,, as already written, all devices already paired work

error was in the configuration.yaml .... whatever was wrong with it .... deleted all the devices there and now I see everything again .... just reassign the names and that's it

It usually happens when you switch to ember the first time, and it actually re-creates its state from the backup : for some minutes, the information is empty. But once the devices are backup, the page will be updated with the proper informations.

there was no change .... that's why i share the information about the error .... because it makes no sense and there was no reason .....

no new gears were learned. after the update everything ran for 2 hours ca..... only then was the list empty! ..

All of those information are read from the MQTT bridge/info topic which are sent to react through websocket.
So for some reasons, you didnt get the message. Restarting z2m in the background will resent the bridge/info message to the frontend (as this is publish at startup, and when device changes).
You should still see the message in MQTT anyway as this is a retained message : if this is not even there, then yes, there is something wrong. If it is there ,but you dont see it in the frontend : probably something happened during the sync/start of react app.