Sometimes the notification chat may fail, and messages read and answered automatically disappear from there. In this case, you can clear the chat manually.
Open the chat and click the “magnifying glass” button in the upper-right corner:
A window opens with the message history. In the upper-right corner, click the button with the trash icon:
Confirm the clearing of the chat by clicking on the button “Delete all the log records”:
The notification history has been deleted: