Chat notification fails


I use TeamViewer (free version 15.45.3) on 5 personal computers. On only one of them, there is no notification of an incoming chat mnessage. Notify me of incoming messages is checked in Options|Account. Opening chat windows, record of chat is shown, so chat was sent, but without notification. Also, in this window, opening gearbox shows Show Notifications as checked. Chat messages are displayed properly on the other 4 computers. All use Windows 10 Pro x64. Also, I cannot submit a support request. As a free user, I am not eligible for TeamViewer support.