Can't save 3D model as library part

[R Muller]

I have been making a number of special railings using small walls, then saving them as library parts. However, there is one rail, in the same model as the others, that I cannot save correctly. The library part is created, but it has only a 2D symbol and no 3D information.

I have tried saving as editable part, non-editable, moving and/or elevating the model, etc. but nothing has worked.

Any other ideas?