Unattended Client tray icon not shwoing on some client PCs

Unattended Client tray icon not shwoing on some client PCs

Hi. Ive having an occassional problem where unattended client PCs don't always show the tray icon. This is often not a problem, however does cause difficulties where the client PC has access disabled. This can usually be fixed by reinstalling the client s/w but recently had a situation where it did not.

What causes this problem and what can i do to reliably fix please...?

Thanks.