As pointed out in this thread (Bug: BFDLACtool not found - wrong path - #3 by Steve63) by @SF_Green, the BFDLAC tool isn’t working when you run it from BFD3.
I found the folder for it at, C:\Program Files (x86)\FXpansion\BFDLACTool and moved it to where BFD was trying to find it, C:\Program Files (x86)\BFD Drums. Opened BFD3 and it now works as it should.