Your KeySCAPE or KeySCAPE LT drawing has been opened in a newer version of AutoCAD, saved back to an older drawing format and you are no longer able to edit KeySCAPE features in your older AutoCAD because they are now Proxy Objects.
KeySCAPE uses Autodesk's advanced AEC object technology that allows you to benefit from automatic updating of the drawing when modifications are made. This same underlying object technology is used by Autodesk for Civil 3D, Autodesk Architecture, Autodesk Mechanical and their other advanced applications. Whilst basic AutoCAD features can revert back, Autodesk does not support the ability to SaveAs and downgrade their AEC technology. This means that when you open a drawing that has been saved back to an older version of AutoCAD, the AEC objects appear as proxy entities - read-only images of the original objects.
If a drawing contains AEC objects from a previous version of AutoCAD, you are warned when opening the drawing that these entities will be upgraded and will no longer be editable in older versions of AutoCAD.
Once saved in the current version the message no longer appears because the underlying objects have been upgraded.
When you choose to SaveAs back to an earlier version of AutoCAD, you are warned again that the AEC objects will no longer be editable in older versions of AutoCAD.
To resolve this, install a compatible version of AutoCAD and set KeySCAPE to run with this version of AutoCAD. (See: KA-01091)
For KeySCAPE LT customers, please upgrade to a newer version of KeySCAPE LT that is using a compatible version of AutoCAD.
AutoCAD 2013 drawing formats are supported by KeySCAPE and KeySCAPE LT running with AutoCAD 2013, 2014, 2015, 2016 and 2017
AutoCAD 2018 drawing formats are supported by KeySCAPE and KeySCAPE LT running with AutoCAD 2018, 2019 and 2020