Loading Some Plugins Unsuccessful: "Plugin dialog class 'ImportForm' appear in multiple assemblies"
Problem:
You are presented a dialog box "Loading Some Plugins Unsuccessful" when opening a model. Inside that dialog the message is:
Failed Loading Plugin:
Plugin dialog class 'ImportForm' appear in multiple assemblies
Assembly:C:\…
Assembly:C:\… <different path>
Remove one of the assemblies or rename one of the classes
Probable Cause:
The installation directory or file name of a extension (Application or Component) has changed and therefore there are two copies (possibly different versions) of the extension in the macro directories.
Solution:
Open the Extension Manager (Applications and components ☰>Manage extensions>Extension manager) and remove one of the extensions listed in the dialog box. Check both versions and remove the unwanted one (probably oldest version). If you can't identify the Application or Component from the file path and name, look for duplicates in the list of installed extensions.
If there are not duplicates in the Extension manager, you may have to manually remove one of the duplicate versions directly in Windows. When manually removing the duplicate assembly, keep a record of the removed record in case the incorrect one is removed.