There are some faces missing from the mask STL files where the original mask was divided. I imported the models into Blender and added a face for those parts. I exported the models to STL files.

I rotated the nub around so that the largest flat surface sits flat on the build plate.

The resulting files are smaller than the originals and my laptop doesn't found like a jet liner trying to do a vertical takeoff. There don't appear to be any errors in the STLs so sending them to cloud print services may work better.

Added a Full Mask model. It will generate errors when loaded into Cura. It does slice properly. The errors are caused by the top and bottom edge loops on the mask parts not being joined together. If you zoom waaaaaaaaaaay in, you can see the gap. On the right side of the mask something is weird about the edges where the original mask was sliced in half to create two parts. The edge loops won't join properly, so I just left them un-joined. The model seems to slice fine in Cura.