Phil, this error is mostly associated with homing/limit switches and reset/feed hold switches.
Check your parameters and make sure that hard limits are off.
Check wiring (loose, frayed, etc.) to your switches (homing, reset, feed hold) and check the switches to see if they are solid and not “bouncy”.
If your switches are not sealed try blowing them out with some compressed air (low pressure).
A soft limit error can cause this message as well.