Status Tray and Status Notifier not showing application icons.
I recently upgraded from Xubuntu 20.04 to Xubuntu 22.04. After the upgrade, both the Status Tray and the Status Notifier (I currently have both on my panel to test this issue) do not display notifier icons for applications started after the panel loads. The network manager icon does appear correctly (presumably since it starts at log in). If I start an application that uses a notifier icon (tested with VLC, KeepassX, Pithos, and Thunderbird using the systray-x plugin), the icon does not appear in either plugin. Restarting the panel with xfce4-panel -r will cause both plugins to correctly display icons for any appropriate application (VLC, etc.) that is running, but closing that application and reopening it does not re-add the notifier icon as expected. xfce4-clipman does correctly display its icon, but that appears to be a systray icon rather than a notifier icon.
I have verified that both plugins have "Hide items by default" unchecked.