No there is not setting to make to fix this. Make sure however you are using the correct (TS) cables to connect the instrument to a proper system. You've given us none of the details about your cabling or sound system, so we will hold off on recommending any action.

We will mention (because it is the most common error) make sure you're physically connecting your cables to the correct jacks... Don't laugh, more people than you realize reach over the top of their keyboard and wind up plugging into a jack that is not an output. Happens at least once a day.

Thanks for the setting info.

Speakers = 1 pair of MR5 Studio monitors
Cables = 1 cable per monitor, no switches or the like.

Regarding connecting the cables, I have double checked things, facing the back side of the Keyboard, repeatedly alternating speakers and input jacks.

It seems very odd that something could have broken, I've only played this keyboard around 5 hours since I purchased it (as new). It's been kept in doors in my living room.

Very odd indeed. We want you to have a good musical experience, so please contact Yamaha Customer Support and get a recommendation on how you should proceed.

Hey, thanks for answering. I do have another question along this line. I noticed today that there are are two other outlets right next to my monitor outlets on the keyboard - they are called "Assignable output" jacks. Might these be used to route all the sound from the keyboard out to the monitors in live time?

No. The Assignable Outputs have a specific use case.

OUTPUT SELECT is normally the Main Left/Right outputs. These are used throughout VOICE mode. Voices can only be directed to the main Left/Right outputs, you use a Pan control to balance the amount to each.

Access to the Assignable Outputs is only available as a PART parameter. This means it is only an option when you are using Performance mode or Multi mode, when Voices are placed in PARTs.

The main L/R outputs are considered "the System" outputs. This means they use the System Effects (Reverb, Chorus), and the Master Effects and Master EQ also only go to the main L/R.

The purpose of the Assignable Outputs is bypass all that (communal) processing and isolate just the individual routed Part. The Voice assigned to a Part keeps its Insert Effects and EQ, but skips all the other processing. Like a direct out on a console, the assignable outputs are pre-fader, pre-effect send, pre-Master Effects, etc.