After printing the prior shown Copic pen holder (attached STL) at 80% infill (custom setting entering 0.8) I printed the ear ring holder which I repaired with Netfabb (attached). I did not change any setting simply wiped the bed with isopropyl and started it. Using Cura, MC did not build the infill.
Thus, I stopped the print and tried the little alien which was also repaired (attached STL). Cura slicer in MC again failed to build the infill.
Thus, I changed the infill from 80% to minimal to "Standard". I did not enter the fraction simply clicked on the standard button. With that Cura slicer in MC did build the infill.
Then, I set a custom infill to "0.4". Cura slicer in MC did build the infill.
Then, I set the custom fill to ".5". Cura slicer in MC did build the infill.
Then, I set the custom fill to ".4". Cura slicer in MC did build the infill.
I will now reprint the ear ring holder without changing any settings.