I just wanted to post this so others might have a current bit of info.
I just spent the better part of two days moving my System from a Dell Laptop to a Dell Desktop, Installed VB 6.1.30 r148432, Extension pak, and updated my guest extension to 6.1.30 on all guest OSs too. Thought all was well. Then I went to debug some code I'm writing, and the standard F-keys did not work in the guest. I was able to confirm this was the same across all 9 guest OSs, a mix of win 7, 10, & 2016 servers. Dug through posts here and the Host forum. Uninstalled/re-installed all VB extensions and VB itself. No change, I tried to use a wired keyboard and it at first failed then started to work, so then I looked at my MX keys found that Logitech now installs another app called Bolt as well as Options app. Removed Bolt, no change.
Opened Options and MX keys has a check box for 'Use F1 - F12 as standard function keys' on the first screen, I checked this option and it corrected the F-Keys issue after I pressed the F-key (F11) multiple times within the guest and now works as it has always worked.
I just wanted others to have a current account of this Logitech induced challenge