Error message for 3MF format
I am getting this error message while trying to import a bookend file for my wife. But with migraine head, my problem solving needs some help please. Any suggestions are welcomed. 
RE: Error message for 3MF format
3mf is not a specific Prusa format. What generated the 3mf you are trying to import ?
There are current compatibility issues with 3mf files saved from bambu/orca slicer for example that lead to messages such as you picture, as they have changed what is stored n the 3mf.
RE: Error message for 3MF format
3mf is not the wonderful interoperability standard you might imagine. Yes, it defines a standard data exchange format for 3D models. But like most interoperability "standards" they don't survive first contact with reality... The 3mf definition is flexible enough to allow for vendor-specific extensions. As a result, a 3mf file saved from one slicer may not work with another. Neophyl's example of Bambulab's slicer and Prusaslicer is one. Or the way Prusaslicer describes added modifiers led to other slicers such as Cura create large blocks where the modifiers where, at least last time I used Cura, which was years ago.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...