CNC USB z axis not starting in correct position.

I have been using the cnc usb controller and software for a few years now with no issues.
Recently ALL my routines that have worked in the past all start the z axis about .25" above what has been defined as zero at the top of the work piece. The z-axis zero is set by mean of a touch plate, again, having been used successfully for a few years. Have I inadvertently done something that has established an offset that has affected ALL my routines?

Help me Obi Wan.... I am not a Jedi yet....

Dakman standing by

SkiPatrol reporting for duty ...

Seems that you are on your own on this one but I am here to make sure that someone answers your post and offers some words of encouragement. The best thing about your situation is that, like you said, it affects all your "routines" therefore it's likely that it is just one thing that needs to be changed back to its original setting. My advice ... go back to the basics and don't run astray. The culprit seems to be the Z-axis and/or how the touch plate is set up. So, look at your Z position values for both the "work" and "machine". On the other side, you can reconfigure your touch plate from scratch. I use TNG so I can't help on the particulars but there is plenty of reference on how to go about it. Test by using the simplest of g-code first and not your routines .... a Z0 move after plate touch-off should put you at the top of the substrate being referenced ... if that works accurately then its not your Z or touch plate but something else. Most likely its something simple ... may the force be with you.