Seems like the reason is that datatypes.library is missing. How did you install WB 3.1 that this library can be missing?
Please check the presence and version of libs:datatypes.library with the List and Version commands like above with window.class. Also check if sys:classes/datatypes directory exists and is filled.
If all is there, please make a new SnoopDOS log for running Utilities/Multiview.
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