Hello Matova,
I don't have experience myself with Dorico, and it's a VST/AU host that we officially support, but it might be compatible anyway if it supports either VST2 plug-ins (Hauptwerk doesn't have a VST3 plug-in), or Audio Unit (AU) plug-ins (if a Mac).
Is it a Mac (given that you mentioned the IAC driver)? If so, if there's a function in Dorico to scan for/enable plug-ins, does it find the Hauptwerk AU plug-in?