I just purchased Dorico and imported an xml finale file. I switched the output from Dorico’s default engine to Note Performer. Playback works unless I try to mute or solo an instrument. When I do this, everything is muted. I looked online and found that this may be due to the fact that all of the instrument assignments are mixed up. The answer talks about HSSE and other things completely unknown to me. What I am hoping to do is receive some simple instructions on what buttons to push in order to fix this issue. My fear is that I will have to dive deeply into learning a huge amount of stuff about sound engineering that is far beyond the scope of simply composing and listening to music. Can anyone help with this by providing a simple solution? Thank you in advance.
Welcome to the forum @dmorriso100 - how did you switch to NotePerformer? Did you use the playback template?
If not, try doing so - this is generally a good first step towards fixing issues with playback sounds.
To mute a single voice in NotePerformer, one must apply the mute in the NP Mixer rather than the Dorico Mixer.
Thank you Lillie, Derek, and Steinberg. I will give your suggestions a try.
Success! Thank you, Lillie, Derrek, and Steinberg!
First, I opened Note performer, clicked on the Dorico icon, in the Attachment to Notation window clicked on Dorico and Repair Connection.
Then I opened Dorico, went to the Play menu, clicked on Playback Template, clicked on Dorico, clicked on Import, and clicked on Apply and Close.
Now it all works using the Dorico Mixer!
I misspoke. In the Playback Template, I clicked on Note Performer. Sorry!
I’m new here and can’t find a way to make a new post! I’m not sure how I did the present one. Anyway, can someone take pity on me and show me how to make a new post? I need advice on how to make a missing piccolo staff reappear. Thank you, and I apologize for my newbie ignorance!
In Setup mode, select the piccolo player, then make sure the Full score layout (on the right) is ticked. This tells Dorico that you want to show the piccolo in the score 
Thank you, Lillie. The Piccolo is back!