I accidentally deleted the base layer but now I can’t place any objects at all. Instead had to start a whole new scene and move everything over. I’m not 100% if it’s a bug but it’s certainly strange.
It seems a little unfortunate.
You need create a new layer, open list of instances, select each instance on by one, and in properties panel on left , select the new layer.
I did start a new layer after deleting the base which is where the issue started. I tried what you mentioned but same thing happened. Couldn’t place objects and adding new objects also did not work. Deleting my added layers didn’t cause this to happen, only when I deleted the Base layer by mistake. Adding new layers and changing properties did not remedy the situation. Once the Base layer was gone it was impossible to place objects even after editing their layer properties.
I ended up starting a new scene and moving my objects there. This is the first time this has happened actually. It wasn’t an important project thankfully.