0 objects changed to layer

Suddenly I’m unable to change the layer of an object. It is a STEP file of a metric 10 mm coupling nut downloaded from McMaster. I opened it in Rhino 5 (Version 5 SR14 64-bit reported as up-to-date) and saved it as a 3dm object, then opened the .3dm in Rhino, copied and pasted into another .3dm model.
When I try to change the layer to an existing layer in the target model, nothing happens other than the notification “0 objects changed to layer…”.
What am I missing?

Never mind! It occurred to me to import the object from the .3dm source into the target. Works fine! Sorry to have troubled anyone.
BTW, I tried to delete the topic but was unable to. I got a notification to contact an administrator.