So I updated Mach4 setting up a new machine, and now all of the sudden my current machine won't run properly.
The motors will not respond/move.
If I restart Mach4 a hand full of times, they will finally respond.
As soon as I try homing, they move to the first or second switch.
At this point the machine stops and I get multiple pop-ups saying "HOMING_PREP failed waiting for FIFO to drain”.
Now nothing works again.

I have no idea what FIFO is.
Can anyone provide any ideas how to correct this issue?

Thanks in advance for any advice.

I have the same problem but some days it does it ...then some days it works good.
I get this error when trying to home.

I had done mutiple reinstalls(Windows and Mach4)...in the end replaced the computer that solved machine crashes, not doing tools changes and spindle not shutting down.
As I was explained to me this is a communication error.
so I have a new ESS board on its way that should take care of this problem...will update as the board is installed.(Next week)

Board replaced same problem 

You may need to decrease the plugin frequency and increase the buffer size. Take a look at this link https://www.warp9td.com/index.php/gettingstarted/setting-up-the-smoothstepper-and-mach4#SetupESSCommunications:~:text=ESS%20Step%202%20%2D%20General%20Tab%3A

You may need to decrease the plugin frequency and increase the buffer size. Take a look at this link https://www.warp9td.com/index.php/gettingstarted/setting-up-the-smoothstepper-and-mach4#SetupESSCommunications:~:text=ESS%20Step%202%20%2D%20General%20Tab%3A pizza tower

This solution works for me. Thank you

The answer to all my problems was the version of Mach4 and the Warp9 plugin.
I uninstalled the latest versions and went through a list of older releases until I got the combination of build and version.
Everrything now works as it should.
I hope this helps out someone else as I was really fustrated with this.

Thanks everyone.