I suspect the problem is simply that the clarinet patch in HSO doesn’t extend sufficiently far downwards to cover the whole range of the bass clarinet: I suggest you open the bass clarinet’s track header in Play mode so you can see which channel in which instance of HALion Sonic SE it’s using, then open the appropriate instance of HSSE, and load the clarinet GM patch instead of the HSO clarinet – the GM patch covers the whole range.