New to Dorico

I am using Dorico for the first time and writing an orchestral score. Everything worked well until I opened the SE3 player to see what it does, and now my symphonic score only plays back the first 16 tracks. What did I do?

In Play mode, in the right hand side VST Instruments panel, make sure you didn’t switch off all except one of the instruments while you were trying to open one.

The left hand button is the “on/off switch,” the middle one shows or hides the display.

If that isn’t the problem, go to the Play menu, Playback Templates and re-select the HSSE template. That should reload the complete playback configuration.