This was observed with the latest version of Remote Utilities Host, as well as all previous versions. This behavior was observed under Windows 10 as well as under Windows 11.
If explorer.exe crashes and is restarted, or if it's being killed and then re-started, the system tray icon is not re-created as it should have been. This is most likely because your programmers have "forgotten" to check for the message WM_TASKBARCREATED and then to re-create the system tray icon with something like "Shell_NotifyIcon(NIM_ADD, &m_tnd);".
The same is true for "Remote Utilities Server", it does not re-create the system tray icon as it should either.
Please fix this, it's a really easy fix!