When a user is trying to access the OLAP cubes in Excel by using Jet Professional or Jet Essentials the following error occurs:
An unexpected error has occurred: Could not load file or assembly 'Microsoft.AnalysisServices.AdomdClient, Version=220.127.116.11...
This is caused by the ADOMD.NET client not being installed. This is normally installed automatically during the installation of the Jet Excel add-in but, if this error comes up, the installation was blocked and it must be installed manually.
Download and install the correct version of the ADOMD.NET client from the Microsoft Download link below on the client machine.