The reason why the message persist, was caused by you having clicked to close the toolbar menu after the first time you got the message *before* the 5-6 timeout message lapsed, so the message got stuck on screen because once the menu is closed, its code gets killed immediately, so it doesn't have a chance to clean the message.
Normally, when you get the message about GSX not being available in cruise, the message is cleared after 5 seconds, and the menu will close itself a second later.