No playback

I receive no playback whatsoever, in any audio device I attempt to run with Dorico. I tried every tip in this video, but nothing worked: https://www.youtube.com/watch?v=5BcPJd92zqU

I am running a MacBook Pro on Mojave 10.14.3 and Dorico Pro 2.2.10 with the HALion Sonic SE 3 and the Orchestra Library installed correctly according to the video. I receive no audio output of any kind, during input or playback. In the VST instruments window, HALion Sonic SE shows up and is turned on. The correct instruments show up pre-loaded in the slots, and I have allotted maximum RAM, 512 voices, and 2 cores for the library to use with no success.

In these efforts, I have successfully gotten the piano (via clicking mouse) to make sound inside of the HALion Sonic SE window, but no sound anywhere else. What am I doing wrong? Have I missed something? Has anyone else had this same issue that could help me?

The fact that you get sound when playing with the mouse on the on-screen keyboard shows, that the audio engine is running and is “connected” properly to the audio interface.
That means that Dorico is sending no MIDI notes to the audio engine. This can happen in a rare case, that Dorico and the audio engine disagree over the currently set sample rate.
Please try the following: Choose Edit > Device Setup and in that dialog change the sample rate to a different value, wait for 3 seconds and then change it back to what it was before.
With this Dorico and audio engine shall get back into sync again.

If that does not help, please load your piano project and then choose Help > Create Diagnostic Report. That will create a zip file on your desktop, please send it to ‘u dot stoermer at steinberg dot de’.