Andi,
I installed the latest VE Pro 6 version, and with it installed, the latest version of Sibelius (8.4.1.111) would not open, but shut down while trying. I tried restarting the computer. Did not help. I reinstalled Sibelius, uninstalled and reinstalled VE Pro 6, and still no luck. Sibelius refused to open.
So I uninstalled VE Pro 6, and downloaded and installed the latest version of VE Pro 5, and everything is back to normal. Sibelius opens and everything is recognized.
I have no idea what the issue is, since Sibelius would not open at all with VE Pro 6. I'll wait until an updated version of VE Pro 6, Sibelius, or OS X before trying again.
I'm happy enough working with VE Pro 5. Perhaps someone else will be able to identify the issue, or it will disappear with various software upgrades.
Randall