Preparing to print but no print starts

[hcdbey]

I have been using a Rostock Max V2 for a few years and today I finished assembling a V3. Some nice additions and changes in the V3 vs V2.

When I select "Print" the status changes to preparing to print but nothing happens. The next message is "Next print".

The Z height calibration has been done as well as the PID. Things basically work. The hot end gets hot. Filament can be extruded. The X, Y & Z motors all work. The print bed gets hot. But it simply won't start a print job or maybe more correctly, it starts the job and finishes the job a few seconds later.

I have tried different STL files. I am using MatterControl Build 1.7.5.9383.

Can someone suggest something that might be wrong?

[rootboy]

Please export a small print to a G code file and put that on your SD card and try that. Also post the .STL and your exported .gcode file here as well.