Brand new to the forums.  My 400 has no brakes right now, front or rear.    Front brake lever has no resistance.   Rear brake pedal has no resistance.
This is new.  Worked fine for a long time.  My son rides it a lot and does not take care of it when he rides, so I discovered it this way.

I have motorcycles and have always bled my own brakes.

Documentation is hard for me to find on bleeding the brakes on this one.  I did discover that the front master reservoir has fluid.  Normal level.
I was able to bleed the 2 front calipers based on one document I found. They bled fine with fresh fluid.  Still no front or rear resistance.

Seems to be related to the rear, so that is next step.   Off to read all I can hear.
Thanks in advance

[2015 Z Force 800 53/Trail EPS]

There were two types of systems on these depending on the year. On both the rear or foot brake peddle applied pressure to both the front and rear calipers and the hand brake just applied pressure to the front. One system has dual chambers in the front calipers and two bleeders for those chambers on each. The other has only a single chamber and one bleeder on the front calipers but has a device in the fluid system that divides the two. That unit has been known to fail and allow fluid to pump back into each master cylinder. Try pushing the peddle down about 3/4s the way and see if you can build pressure with the hand lever...and visa-versa. If so, that unit needs replaced and the system reverse bled. If yours is one with the dual chambers, and there is no leeks and no air in the system. Then as unlikely as it might be..I would have to say both masters have failed.