So after about 1.5 years, this problem reappeared today.
Machine has been running no problems, then at the end of a tool change, the spindle braking did not work. Instead I got the below "Spindle Stop" error, and the spindle coasted to a stop after several minutes.
Attachment 455350
I shut down and restarted everything, and the spindle timed out without running. This time it gave me the same Spindle Drive Not Ready as in my first post here.
Attachment 455352
Next, I shut it down again, restarted, this time it worked testing through MDI. So I restarted program, it successfully indexed and changed a tool, ran that one tool, and worked fine until shutdown before tool change. Then it gave the same Spindle Stop error as before. A new restart and it won't even index the spindle to do a tool change.
Going with the previous suggestions, I checked relays C24 & C25. C24 is off and open, C25 is on and closed. So if the previous information was correct and both must be on, then whatever controls C24 is the likely issue. But this puts me back at the same issue I always have when this machine gives problems. I am very good at electro-mechanical troubleshooting, but without more documentation, troubleshooting this is nearly impossible.
If anyone can help here, I am dead in the water.