Decals created with earlier DECALmachine versions, such as 1.4.2, 1.8 or 1.9 need to be updated before they can be used in DECALmachine 2.0.
The tools to do so are located in the the Update Decals panel.
You can skip updating Decals from version 1.4.2, by deleting a Decal's icon.
To skip updating Decals from version 1.8/1.9, just remove the Decal's folder.
Decals from DECALmachine 1.4.2
Decals from DECALmachine 1.8/1.9
Once you've updated your Decal libraries, you can proceed to the next page, to learn how to update Blend files using the previous Decals too.