If the printhead is moving in the designated patterns, but not extruding, it may be that your G-code is written for a different printhead than is being used. This would not apply if you are directly uploading a .STL file.

The Bio X post processor will fix the motion if you accidentally use the printhead not designated in your code. For example, if you used the second printhead, but your G-code refers to T0 (printhead #1), then the printer will switch the movements to the second printhead rather than the first specified. However, the post processor does not switch the extrusion commands as well.

In summary, if you are experiencing issues in which the printhead is moving as specified in the G-code but not extruding, it may be that you are not using the printhead that was declared in your G-code.