@camilo7QSK2 wrote:
The family is too big to upload it.
@camilo7QSK2
If thats a face based fixture...probably you have hosted on the wrong work plane or Face...Try the flip work plane see if that helps

If it is a wall based, the error message implies there’s some sort constraints issues within the family itself. This could be preventing the instance—or parts of it (e.g., a poorly constrained extrusion)—from being created, and is likely also causing issues when attempting to delete it. For instance, the family is constrained in a way which did not consider the changing thickness of the wall; hence, when you created a new type with a different over all built up thickness it broke the family
Cannot tell for sure unless you upload something to check . A file containing just a wall and a sconce shouldn't be too large to share. Simply select the wall and the sconce in your model, paste them into a new empty project, purge, save, and upload the file.