RonC wrote
Problem has been resolved. For benefit of other mizuphone users seeing this thread in a search:
As well, for future reference, both I and readers of this thread will know how to identify a failure due to incompatible codecs, and how to resolve it.
The solution from mizutech technicians was better than I thought: after installing and testing the non-free version, as suggested, the free version began to work normally. The technicians will know better than I if the free version may be using codecs installed by the paid version. For personal (non-business) use, the free version really has all I need, so I am most grateful.