How are you launching LL Hub. Through the command line or the UI?
We just noticed a typo in the Docs for the command line. The beginning quotes are going the wrong way, lol. Try this:
[your install directory]\Engine\Binaries\LiveLinkHub.exe -EnablePlugins=“LiveLinkFreeD,LiveLinkPrestonMDR,LiveLinkMasterLockit,LiveLinkVRPN”