There is a switch for 'Show Scroll Bars' in File/Preferences/Display.
It's hard to see how a simple version update would change this setting though. Did you update from a MUCH older version of Sibelius? Anyway, check that setting.
I've been using scroll bars in Sib since day one, because I hated the navigator. But I cannot remember how I originally turned them on. Searching Google, I discover that the switch should be located on the View tab, but I cannot find it there. I'd hate to lose this facility. Ah, yes, thanx, Laurence. Preferences/Display. Command Search was no help.