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Sounds like something was done to the models after importing that removed material data.  I would recommend deleting the models in your Unity project, then dragging the models directly from the folder into your unity project and try again.  I've imported this collection successfully.  Also, this is a MAST question.  Might be better in forum for that tool or on the Discord server.

thanks for the quick response I did just that and it works now, thanks!