The warning mark on an IK constraint typically indicates a problem with the constraint's setup in relation to skins. According to the Spine User Guide, a warning is shown on a constraint's tree icon if the constraint's target bone is in a skin, but the constraint itself is not in that skin, or if all of the constraint's constrained bones are in skins, but the constraint is not in any of those skins. To resolve this, ensure that the constraint is added to the same skins as the target bone. Additionally, if all constrained bones are in skins, make sure the constraint is included in at least one of those skins.
