I tested the websocket in JS and it connects and receives messages just fine and they also get logged in the notification-server.log
my assumption is that the client does not even try to connect to the websocket after calling /notification/ping
A recent test can confirm that. The /notification/ping endpoint get called right on startup of the seafile desktop app but not the /notification endpoint. Nevertheless, the /notification endpoint gets called right when you quit the the app. In the example beneath i opend the app and closed it right afterwards. The second log does not appear when you start it and leave it open. Only on close.
xx.xx.xx.xx- - [04/Aug/2023:23:50:20 +0200] "GET /notification/ping HTTP/1.1" 200 16 "-" "Seafile/9.0.2 (Windows NT)" xx.xx.xx.xx- - [04/Aug/2023:23:50:33 +0200] "GET /notification HTTP/1.1" 101 44 "-" "-"