New user cannot get stl file to slice

[LoganOhio 0]

I have an Ender 3Pro printer.  I have used Cura 4.8 successfully once slicing stl files provided with printer.  However, I cannot get my own first STL file to slice.  I read that the scale can be off and have corrected it so that the mm are correct and within envelope size.  But nothing shows up on the preview other than the gray silhouette on build platform.  Not sure what I am doing wrong because the program is still giving me error message when slicing.

 

CE3PRO_Male qtr turn Ver C.3mf

[GregValiant 1,330]

Select the part.  Select the movement tool from the left toolbar and set the "Z" to zero.  After scaling, or during some other operations, the part will seem to hover in the air.