[Offline plug-in error – CRM 2016] Unable to load plug-in assembly OR Public key token [PUBLIC KEY TOKEN ID] is not found in allow list.

Recently we had an issue when we configure CRM 2016 to Outlook for offline functionality. We got an “Unable to load plug-in assembly” error. 

Root cause: Microsoft applies additional security restriction to registered offline plug-in assemblies. When Microsoft Dynamics 365, Dynamics CRM 2016 or Dynamics CRM Online for Microsoft Office Outlook Access is installed, an AllowList key is added to the system registry on the client computer. For each assembly containing offline plug-in that you register, we must add a registry sub-key under AllowList key with the key name derived from the assembly’s public key token.

Solution:

1)    Get the public key token.

·         Load assembly which contain offline plug-in

·         Select plug-in assembly in tree view of tool.

·         Copy public key token.

2)    Add an AllowList key

·         Open Registry Editor by selecting start, then Run and type regedit.exe

·         In the tree view panel navigate to AllowList key. The complete path of the key is

·         HKEY_CURRENT_USER\Software\Microsoft\MSCRMClient\AllowList.

·         Select AllowList key and right click on it to display the context menu.

·         Select New then click Key to create new sub-key

·         Paste public key token value into the name of the new sub-key

·         Close the registry editor.