Sound Issues in Only One Piece

I need help concerning playback on a few instruments in particular.
I sometimes write pieces that use a multitude of instruments, some with full string quartets and some just solo piano; these have always been fine and have only needed me to restart Musescore or my computer to regain sound if there has been a problem. However, with a current piece I'm putting together, neither electric guitar, bass guitar or drums make any sound at all. This only goes for the latest update of Musescore 3 (3.4.3.9788) as far as I'm aware, and Musescore 2 runs the original piece just fine (before I started adding the aforementioned instruments).
I have run myself through everything in the How-To for restoring sound if playback stops working to no avail, as the synthesiser works fine, I have restarted all audio devices, et cetera. The only think I've been unable to do is attempt updating the sound drivers to 64-bit as I have found no clear way to do so, and in my sound card settings in the control panel I cannot find anthing that says "advanced", so I haven't found "Allow applications to take exclusive control of this device"...
Surprisingly, I am (most likely) not missing the sound samples for the instruments themselves - when I click on a single note or chord, it sounds just fine. I am not sure how to proceed, as I'm not sure what the actual issue is.
I'm running on a 64-bit Windows 10 laptop.
Thank you in advance. Sorry for the long message.