The object itself could be locked rather than locking the layer.
Does it have grey selection handles when you select it?
Or it could be a MEP object that you can only edit if you have the MEP add-on loaded.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11