Loading Some Plugins Unsuccessful: "Plugin dialog class 'ImportForm' appear in multiple assemblies"

Tekla Structures
Not version-specific
Tekla Structures
Plugin dialog class
Plugin multiple assemblies
Duplicate extension
Failed Loading Plugin
class 'ImportForm'
appear in multiple assemblies
Tekla.EPM.Plugin.dll
TeklaEPMPlugin.dll
Remove one of the assemblies or rename one of the classes
Environment
Not environment-specific

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

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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.

Image
Open the Extension manager by going to the three horizontal line (hamburger) menu inside the Applications and components pane, then Manage extensions, then Extension manager. In the Extension manager, locate duplicate extension and remove one. You must restart Tekla Structures to complete.
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