Listed below are the most common errors that may be encountered when installing and licensing the Charcoal Editor plug-in. If you are unable to resolve your installation issues using this guide, please do not hesitate to contact me.
Charcoal Editor Does Not Display in the Plug-in Manager
Ensure that CharcoalEditor.mll (Windows) or CharcoalEditor.bundle (OSX) exists in Maya's default plug-ins directory or in a directory included in MAYA_PLUG_IN_PATH.
To verify that a directory is included in the MAYA_PLUG_IN_PATH variable, run the following MEL command:
Loading Charcoal Editor in the Plug-in Manager Fails
When Maya fails to load a plugin an error is generated and displayed in the script editor. Listed below are the most common errors and the likely cause.
Error: "CharcoalEditor" was compiled against too old a version of the Maya API and is thus incompatible with the current Maya version.
The wrong version of the plug-in is being loaded (e.g. loading Charcoal Editor for Maya 2012 in Maya 2013). Copy the correct version of Charcoal Editor to the plug-ins folder.
Error: The specified procedure could not be found. (CharcoalEditor)
The wrong version of the plug-in is being loaded (e.g. loading Charcoal Editor for Maya 2011 in Maya 2013). Copy the correct version of Charcoal Editor to the plug-ins folder.
The most common cause of an error that only displays the plug-in name is when the 32-bit plug-in is loaded in a 64-bit version of Maya (or vice-versa). Confirm that the version of Maya and the Charcoal Editor plug-in match.
Invalid license errors should be rare and are often caused by inadvertent changes to license file. Even small changes to the license file will render it invalid.
To restore your license, locate the email containing your original license and download/overwrite the file on your hard drive. Launch Maya and reload the license.
Maya 2011: For users of Maya 2011, there is a bug in releases prior to Service Pack 1 that will result in an invalid license.
To verify the version, select About Maya from the main menu (Help->About Maya). Service Pack 1 can be downloaded from the Autodesk website.